Compositions for eliciting an immune response

ABSTRACT

The invention is directed to the use of (i) a first antigen corresponding to a target antigen of interest, together with (ii) a second antigen, corresponding to a modified form of the target antigen, whose rate of intracellular proteolytic degradation is increased, enhanced or otherwise elevated relative to the first antigen, in compositions and methods for inducing both humoral and cellular immunity in an individual. The ability to provide compositions, which are capable of inducing both host-protective antibody and cell-mediated immune responses, facilitates the generation of immunogenic compositions capable of combating, inter alia, conditions that have long latency periods and, therefore, benefit from the dual approach of prophylaxis and therapy in one delivery.

FIELD OF THE INVENTION

THIS INVENTION relates generally to compositions and methods for preventing and treating a disease or condition. More particularly, the present invention contemplates a method for the manufacture of a medicament exhibiting increased efficacy in prophylactic and therapeutic applications. Even more particularly, the present invention provides molecules which are capable of inducing both humoral and cellular immunity and provides for their use as a means for eliciting such immunity in an individual. The present invention further contemplates methods for cell-specific or tissue-targeted delivery of polynucleotide and/or polypeptide immunogens, capable of inducing simultaneously neutralising antibody and cell-mediated immune responses. Cells or tissues containing the polynucleotides also form part of the present invention. The ability to provide compositions capable of inducing both host-protective antibody and cell-mediated immune responses facilitates the generation of immunogenic compositions capable of combating, inter alia, conditions that have long latency periods and, therefore, benefit from the dual approach of prophylaxis and therapy in one delivery.

Bibliographic details of the publications numerically referred to in this specification are collected at the end of the description.

BACKGROUND OF THE INVENTION

New approaches for intervention in virally-induced disease are always sought after. Interest has been shown in adapting gene therapy for use in delivery of DNA immunogens to target cells and tissues. Success in this endeavour has been limited, however, partly because selective delivery of genes to target tissues has proven to be extremely difficult, and partly because success is dependent upon being able to predictably elicit either a specific antibody response or a cell-mediated response or both. Which response is desired, depends on the nature of the presenting problem.

While use of tissue-specific promoters to target gene therapy has been effective in some animal models, it has proven less so in man and selective tissue-specific promoters are not available for a wide range of tissues. Gene delivery systems such as vectors are not themselves tissue selective. Viral vectors, such as retroviruses and adenovirus, may be used and are to some extent selective. However, many vector systems are by their nature unable to produce stable integrants. Moreover, some also invoke immune responses themselves, thereby precluding predictable and effective immunological intervention.

A further reason why gene therapy has proven to be difficult is the unpredictability of the kind of immune response which can be generated as a result of delivery of packaged DNA, by whatever means, to a cell or tissue. For example, it is known that DNA vaccines delivered to the skin tend to cause the induction of antibodies, whereas the same vaccine delivered intramuscularly may favour a cellular response. In instances where virus infection is associated with long latency periods, such as is the case, for example, with infection by human immunodeficiency virus and herpes simplex virus, it may be desirable to be able to elicit responses from both arms of the immune system to allow simultaneous protection against future infection and treatment of existing infection.

One example where the unpredictability of the response is of concern is in attempts to overcome the effects of infection by the human papilloma virus (HPV). Many genotypes of HPV are known to be antecedent to ano-genital malignancy¹; tumours can develop after a latency period of from 10 to 30 years. There is a need, therefore, to find means to induce both neutralising antibody to prevent HPV infection, and cell-mediated immunity to treat existing infection. Induction of a cell-mediated immune response to viral genes is desirable both to control existing infection and, particularly, to eliminate the premalignant consequences of HPV infection. A vaccine, which was capable of effecting both humoral and cellular immunity, would constitute a major advance in medicine's capability to intervene effectively in such disease conditions.

Recent attempts to increase the level of cellular response following DNA immunisation have had some success through conjugation of the sequences encoding the cellular protein ubiquitin. DNA immunisation as a form of gene therapy is a relatively new approach to vaccination. In theory, and sometimes in practice, the inoculated plasmid DNA enters the cell and the encoded proteins are expressed therein. In this way, access of the antigen to the major histocompatibility complex (C) class I antigen presentation pathway is more likely to occur. In some cases, enhanced Cytotoxic T Lymphocyte (CTL) responses have been shown following ubiquitination^(31,32). However, ubiquitination is known not to enhance the immunogenicity of all polynucleotide vaccines³⁵. Furthermore, the increased CTL response is sometimes at the expense of immunogenicity and production of neutralising antibody³³.

Furthermore, the present inventors have previously shown that the L1 major capsid protein of HPV can self-assemble into virus-like particles (VLPs)³. Used as a vaccine, VLPs elicit conformation-dependent host-protective neutralising antibody⁴. However, papilloma virus (PV) infection is often persistent, and 20-50% of HPV-infected individuals do not develop PV-specific immunity⁵⁻⁷, suggesting that PV infection is seen poorly by the immune system⁸. The capsid genes of HPV have been shown to have sub-optimal codon usage for expression in mammalian cells¹².

SUMMARY OF THE INVENTION

The present invention is predicated in part on a novel strategy for raising a more efficacious immune response against a target antigen. The strategy involves the use of (i) a first antigen corresponding to the target antigen, together with (ii) a second antigen, corresponding to a modified form of the target antigen, whose rate of intracellular proteolytic degradation is increased, enhanced or otherwise elevated relative to the first antigen. As more fully described hereinafter, the present strategy is used advantageously to elicit simultaneously prophylactic and/or therapeutic levels of humoral and cellular responses against an antigen of interest to combat, inter alia, conditions that have latency periods and, therefore, benefit from the dual approach of prophylaxis and therapy.

Thus, in one aspect of the present invention, there is provided a composition for eliciting a humoral and a cellular immune response against a target antigen, comprising a first antigen corresponding to the target antigen, or a polynucleotide from which the first antigen is expressible, together with a second antigen corresponding to a modified form of the target antigen, wherein the rate of intracellular proteolytic degradation of the second antigen is increased, enhanced or otherwise elevated relative to the first antigen, or a. polynucleotide from which the second antigen is expressible.

In another aspect, the invention contemplates a composition for eliciting a humoral and a cellular immune response against a target antigen, comprising at least one polynucleotide from which is expressible a first antigen corresponding to the target antigen and a second antigen corresponding to a modified form of the target antigen, wherein the rate of intracellular proteolytic degradation of the second antigen is increased, enhanced or otherwise elevated relative to the first antigen.

In yet another aspect, the invention encompasses a composition for eliciting a humoral and a cellular immune response against a target antigen, comprising a first antigen corresponding to the target antigen and a second antigen corresponding to a modified form of the target antigen, wherein the rate of intracellular proteolytic degradation of the second antigen is increased, enhanced or otherwise elevated relative to the first antigen.

In still yet another aspect, the invention extends to a composition for eliciting a humoral and a cellular immune response against a target antigen, comprising a first antigen corresponding to the target antigen and a polynucleotide from which a second antigen corresponding to a modified form of the target antigen is expressible, wherein the rate of intracellular proteolytic degradation of the second antigen is increased, enhanced or otherwise elevated relative to the first antigen.

In another aspect, the invention envisions a composition for eliciting a humoral and a cellular immune response against a target antigen, comprising a polynucleotide from which a first antigen corresponding to the target antigen is expressible, together with a second antigen corresponding to a modified form of the target antigen, wherein the rate of intracellular proteolytic degradation of the second antigen is increased, enhanced or otherwise elevated relative to the first antigen.

Suitably, the intracellular proteolytic degradation is proteasome-mediated.

Preferably, the intracellular proteolytic degradation is ubiquitin-mediated.

Preferably, the second antigen comprises, or is otherwise associated with, an intracellular degradation signal or degron. In one embodiment, the intracellular degradation signal comprises a destabilising amino acid at the amino-terminus of the second antigen. In a preferred embodiment of this type, the destabilising amino acid is selected from isoleucine and glutamic acid, more preferably from histidine tyrosine and glutamine, and even more preferably from aspartic acid, asparagine, phenylalanine, leucine, tryptophan and lysine. In an especially preferred embodiment, the destabilising amino acid is arginine. In another preferred embodiment of this type, the second antigen is fused or otherwise conjugated to a masking entity, which masks said amino terminus so that when unmasked the second antigen will exhibit the desired rate of intracellular proteolytic degradation. Suitably, the masking entity is a masking protein sequence. The masking protein sequence is preferably cleavable by an endoprotease, which is suitably an endogenous endoprotease of a mammalian cell. For example, an endoprotease cleavage site may be interposed between the masking protein sequence and the second antigen. Suitable endoproteases include, but are not restricted to, serine endoproteases (e.g., subtilisins and furins), proteasomal endopeptidases, proteases relating to the MHC class I processing pathway and signal peptidases. In a preferred embodiment of this type, the masking protein sequence comprises a signal peptide sequence. Suitable signal peptides sequences are described, for example, by Nothwehr et al. (1990, Bioessays 12 (10): 479-484), Izard, et aL (1994, Mol. Microbiol. 13 (5): 765-773), Menne, et al. (2000, Bioinformatics. 16 (8): 741-742) and Ladunga (2000, Curr. Opin. Biotechnol. 11 (1): 13-18).

Alternatively or in addition, the intracellular degradation signal comprises an ubiquitin acceptor, which allows for the attachment of ubiquitin by intracellular enzymes, which target the second antigen for degradation via the ubiquitin-proteosome pathway. Suitably, the ubiquitin acceptor is a molecule which contains a residue appropriately positioned from the amino terminus of the second antigen as to be able to be bound by ubiquitin molecules. Such residues preferentially have an epsilon amino group such as lysine. In a preferred embodiment of this type, the ubiquitin acceptor comprises at least one, preferably at least two, more preferably at least four and still more preferably at least six lysine residues, which are suitably present in a sufficiently segmentally mobile region of the second antigen.

In another embodiment, the intracellular degradation signal comprises a ubiquitin or biologically active fragment thereof. In a preferred embodiment of this type, the ubiquitin or biologically active fragment thereof is fused, or otherwise conjugated, to the second antigen. Suitably, the ubiquitin is of mammalian origin, more preferably of human or other primate origin. In a preferred embodiment of this type, the ubiquitin comprises the sequence set forth in SEQ ID NO: 2. In an alternate embodiment, the ubiquitin comprises two or more copies the sequence set forth in SEQ ID NO: 2.

The target antigen is suitably refractory or resistant to intracellular proteolytic cleavage, which is preferably associated with a poor or otherwise ineffective cytotoxic T lymphocyte (CTL) response. The target antigen may correspond to at least a portion of a protein to which an immune response is desired. Preferably, the target antigen corresponds to at least a portion of a structural protein. Suitably, the structural protein is a protein of a pathogenic organism (e.g., viral, bacterial, fungal, protozoan). In a preferred embodiment of this type, the structural protein is a viral protein, which is preferably a capsid protein or capsomer. Preferably, the viral capsid protein is a capsid protein of a crystalline virus. Examples of suitable viral capsid proteins include, but are not restricted to, the L1 and/or L2 proteins of papillomavirus, the capsid proteins of a Herpesvirns (e.g., GpD and GpB), VP1-3 of polyomavirus, VP1-6 of blue tongue virus, Hepatitis B surface antigen, Hepatitis C surface antigen, the capsid proteins of Parvovirus, the capsid proteins of Yeast Ty particles, the capsid proteins of Retroviruses (e.g., HIV and RSV), the capsid proteins of Rotavirus, the capsid proteins of Coronaviruses, and the capsid proteins of Adenovirus. In a preferred embodiment, the capsid protein is a papillomavirus (PV) capsid protein. The PV capsid protein is suitably selected from L1 and L2 capsid proteins.

The composition may further comprise an adjuvant. Preferably, the adjuvant delivers the antigens, preferably the second antigen, to the class I major histocompatibility MHC) pathway. For example, such adjuvants include, but are not limited to, saponin-containing compounds (e.g., ISCOMs) and cytolysins, which mediates delivery of antigens to the cytosol of a target cell. The cytolysin may be linked to, or otherwise associated with, one or both of said antigens. The cytolysin preferably mediates transfer of the antigens from the vacuole (e.g., phagosome or endosome) to the cytosol of the target cell and in a preferred embodiment of this type, the cytolysin is a listeriolysin.

In another aspect, the invention resides in a nucleic acid composition for eliciting a humoral and a cellular immune response against a target antigen, comprising:

-   -   a first polynucleotide encoding a first antigen corresponding to         the target antigen; and     -   a second polynucleotide encoding a second antigen, corresponding         to a modified form of the target antigen, whose rate of         intracellular proteolytic degradation is increased, enhanced or         otherwise elevated relative to the first antigen;     -   wherein said first polynucleotide and said second polynucleotide         are operably linked to a regulatory polynucleotide.

In yet another aspect, the invention encompasses a nucleic acid composition for eliciting a humoral and a cellular immune response against a target antigen, comprising:

-   -   a first polynucleotide encoding a first antigen corresponding to         the target antigen; and     -   a second polynucleotide encoding a second antigen, corresponding         to a modified form of the target antigen, whose rate of         intracellular proteolytic degradation is increased, enhanced or         otherwise elevated relative to the first antigen;     -   wherein said first polynucleotide and said second polynucleotide         are operably linked to different regulatory polynucleotides.

In a further aspect, the invention contemplates a nucleic acid composition for eliciting a humoral and a cellular immune response against a target antigen, comprising:

-   -   a synthetic construct comprising a first polynucleotide, which         encodes a first antigen corresponding to the target antigen, and         which is operably linked to a regulatory polynucleotide; and     -   another synthetic construct comprising a second polynucleotide         encoding a second antigen, which corresponds to a modified form         of the target antigen, whose rate of intracellular proteolytic         degradation is increased, enhanced or otherwise elevated         relative to the first antigen, wherein said second         polynucleotide is operably linked to a regulatory         polynucleotide.

In one embodiment, the second polynucleotide comprises a first nucleic acid sequence, which encodes an antigen corresponding to the target antigen, and which is linked in reading frame with a second nucleic acid sequence encoding a ubiquitin or biologically active fragment thereof. In a preferred embodiment of this type, the second polynucleotide comprises a first nucleic acid sequence, which encodes an antigen corresponding to the target antigen, and which is linked downstream of, and in reading frame with, a second nucleic acid sequence encoding a ubiquitin or biologically active fragment thereof. In another embodiment of this type, the second polynucleotide comprises a first nucleic acid sequence, which encodes an antigen corresponding to the target antigen, and which is linked upstream of, and in reading frame with, a second nucleic acid sequence encoding a ubiquitin or biologically active fragment thereof. Preferably, but not exclusively, the ubiquitin-encoding nucleic acid sequence comprises the sequence set forth in SEQ ID NO: 1.

In another embodiment, the second polynucleotide comprises a first nucleic acid sequence encoding an antigen, which corresponds to the target antigen, and which is modified to include a destabilising amino acid at its amino-terminus, wherein said first nucleic acid sequence is linked downstream of, and in reading frame with, a second nucleic acid sequence encoding a masking protein sequence.

In one embodiment, the first polynucleotide and/or the second polynucleotide is codon optimised to permit enhanced expression of an antigen encoded thereby in a target cell.

In another embodiment, the first polynucleotide and/or the second polynucleotide is codon optimised to permit higher expression of the antigen encoded thereby in a target cell than in another cell.

The nucleic acid composition may optionally comprise a pharmaceutically acceptable carrier and/or diluent or an adjuvant as broadly described above.

The nucleic acid compositions as broadly described above may be in the form of one or more synthetic constructs.

The invention further contemplates a host cell containing the synthetic construct or synthetic construct system as broadly described above.

In still another aspect, the invention provides a method of eliciting a humoral and a cellular immune response against a target antigen, comprising:

-   -   contacting at least one recipient cell with a composition         comprising a first antigen corresponding to the target antigen,         and a second antigen, corresponding to a modified form of the         target antigen, whose rate of intracellular proteolytic         degradation is increased, enhanced or otherwise elevated         relative to the first antigen,     -   whereby said first antigen and said second antigen are expressed         together in the same recipient cell or expressed separately in         different recipient cells.

According to another aspect, the invention provides a method of eliciting a humoral and a cellular immune response against a target antigen, comprising:

-   -   contacting at least one recipient cell with a nucleic acid         composition as broadly described above, whereby said first         antigen and said second antigen are expressed together in the         same recipient cell or expressed separately in different         recipient cells.

Suitably, the nucleic acid composition is produced by:

-   -   optimising the codon composition of a parent polynucleotide         encoding an antigen selected from the group consisting of the         first antigen and the second antigen to construct a codon         optimised polynucleotide whereby expression of the antigen from         the codon optimised polynucleotide in said at least one         recipient cell is increased, enhanced or otherwise elevated         relative to that from said parent polynucleotide.

In one embodiment, the codon composition is optimised by:

-   -   selecting a first codon of the parent polynucleotide for         replacement with a synonymous codon, wherein the first codon is         selected on the basis that it has a higher translational         efficiency than said synonymous codon in said at least one         recipient cell, and     -   replacing said first codon with said synonymous codon to         construct said codon optimised polynucleotide.

In an alternate embodiment, the codon composition is optimised so that the antigen is expressible at a higher level in said recipient cell than in another cell. In a preferred embodiment of this type, the codon composition is optimised by:

-   -   selecting a first codon of the parent polynucleotide for         replacement with a synonymous codon which has a higher         translational efficiency in said recipient cell than in said         other cell; and     -   replacing said first codon with said synonymous codon to form         said codon optimised polynucleotide.

The recipient cell(s), which is contacted with the composition, is preferably an antigen-presenting cells, which is suitably selected from a dendritic cell, a macrophage or a B cell.

In yet another aspect, the invention extends to a composition of matter for eliciting a humoral and a cellular immune response against a target antigen, comprising antigen-presenting cells which have been contacted with a first antigen corresponding to the target antigen or with a polynucleotide from which the first antigen is expressible, and with a second antigen corresponding to a modified form of the target antigen, whose rate of intracellular proteolytic degradation is increased, enhanced or otherwise elevated relative to the first antigen or with a polynucleotide from which the second antigen is expressible, for a time and under conditions sufficient to express a processed form of said first antigen, and a processed form of said second antigen, for presentation to, and modulation of, T cells.

Suitably, the composition of matter further includes an adjuvant.

Suitably, the T cells are cytotoxic T lymphocytes (CTLs).

In still yet another aspect, the invention resides in a method of delivering an antigen to antigen-presenting cells for the production of antigen-primed antigen-presenting cells useful for eliciting a humoral and a cellular immune response against a target antigen, said method comprising:

-   -   contacting antigen-presenting cells with a first antigen         corresponding to the target antigen or with a polynucleotide         from which the first antigen is expressible, and with a second         antigen corresponding to a modified form of the target antigen,         whose rate of intracellular proteolytic degradation is         increased, enhanced or otherwise elevated relative to the first         antigen or with a polynucleotide from which the second antigen         is expressible, for a time and under conditions sufficient to         express a processed form of said first antigen, and a processed         form of said second antigen, for a time and under conditions         sufficient to permit said antigens to be internalised by the         antigen-presenting cells.

The antigen-presenting cells may be contacted in vivo or in vitro and are suitably selected from dendritic cells, macrophages and B cells. Preferably, the antigen-presenting cells are dendritic cells.

In a further aspect of the invention, there is provided a method for producing antigen-primed antigen-presenting cells for eliciting a humoral and a cellular immune response against a target antigen, comprising:

-   -   contacting antigen-presenting cells with a first antigen         corresponding to the target antigen or with a polynucleotide         from which the first antigen is expressible, and with a second         antigen corresponding to a modified form of the target antigen,         whose rate of intracellular proteolytic degradation is         increased, enhanced or otherwise elevated relative to the first         antigen or with a polynucleotide from which the second antigen         is expressible, for a time and under conditions sufficient to         express a processed form of said first antigen, and a processed         form of said second antigen, for a time and under conditions         sufficient to permit said antigens to be internalised by the         antigen-presenting cells; and     -   culturing the antigen-presenting cells for a time and under         conditions sufficient for said first and said second antigens to         be processed for presentation by the antigen-presenting cells.

Suitably, the above method further comprises isolating antigen-presenting cells from a heterogeneous population of cells.

In a further aspect of the invention, there is provided a method for modulating an immune response, comprising administering to a patient in need of such treatment a composition as broadly described above.

According to a still further aspect of the invention, there is provided a method for treatment and/or prophylaxis of a disease or condition, comprising administering to a patient in need of such treatment an effective amount of a composition as broadly described above.

A further aspect of the present invention is directed to a method for eliciting a humoral and a cellular immune response against a target antigen, comprising coadministering to a patient:

-   -   a first antigen corresponding to the target antigen, or a         polynucleotide from which the first antigen is expressible; and     -   a second antigen corresponding to a modified form of the target         antigen, wherein the rate of intracellular proteolytic         degradation of the second antigen is increased, enhanced or         otherwise elevated relative to the first antigen, or a         polynucleotide from which the second antigen is expressible.

In yet another aspect, the invention contemplates a method for eliciting a humoral and a cellular immune response against a target antigen, comprising coadministering to a patient:

-   -   a polynucleotide from which a first antigen, corresponding to         the target antigen, is expressible; and     -   a polynucleotide from which a second antigen, corresponding to a         modified form of the target antigen, is expressible, wherein the         rate of intracellular proteolytic degradation of the second         antigen is increased, enhanced or otherwise elevated relative to         the first antigen.

In still yet another aspect, the invention encompasses a method for eliciting a humoral and a cellular immune response against a target antigen, comprising coadministering to a patient:

-   -   a first antigen corresponding to the target antigen; and     -   a polynucleotide from which a second antigen, corresponding to a         modified formn of the target antigen, is expressible, wherein         the rate of intracellular proteolytic degradation of the second         antigen is increased, enhanced or otherwise elevated relative to         the first antigen.

In a further aspect, the invention resides in a method for eliciting a humoral and a cellular immune response against a target antigen, comprising coadministering to a patient:

-   -   a polynucleotide from which a first antigen, corresponding to         the target antigen, is expressible; and     -   a second antigen corresponding to a modified form of the target         antigen, wherein the rate of intracellular proteolytic         degradation of the second antigen is increased, enhanced or         otherwise elevated relative to the first antigen.

In still a further aspect, the invention provides a method for eliciting a humoral and a cellular immune response against a target antigen, comprising coadministering to a patient:

-   -   antigen-presenting cells which have been contacted with a first         antigen corresponding to the target antigen, or with a         polynucleotide from which the first antigen is expressible, for         a time and under conditions sufficient to express a processed         form of said first antigen for presentation to, and modulation         of, T cells; and     -   antigen-presenting cells which have been contacted with a second         antigen, corresponding to a modified form of the target antigen,         whose rate of intracellular proteolytic degradation is         increased, enhanced or otherwise elevated relative to the first         antigen, or with a polynucleotide from which the second antigen         is expressible, for a time and under conditions sufficient to         express a processed form of said second antigen for presentation         to, and modulation of, T cells,     -   wherein the antigen-presenting cells which have been contacted         with the first antigen and the antigen-presenting cells which         have been contacted with the second antigen may be the same or         different.

In still another aspect, the invention provides a method for eliciting a humoral and a cellular immune response against a target antigen, comprising coadministering to a fpatient:

-   -   antigen-presenting cells which have been contacted with a first         antigen corresponding to the target antigen, or with a         polynucleotide from which the first antigen is expressible,         together with a second antigen, corresponding to a modified form         of the target antigen, whose rate of intracellular proteolytic         degradation is increased, enhanced or otherwise elevated         relative to the first antigen, or with a polynucleotide from         which the second antigen is expressible, for a time and under         conditions sufficient to express a processed form of said first         antigen and a processed form of said second antigen for         presentation to, and modulation of, T cells.

In a further aspect, the invention extends to the use of a first antigen or a polynucleotide from which the first antigen is expressible, together with a second antigen or a polynucleotide from which the second antigen is expressible, in the preparation of a medicament for the treatment of a disease or condition associated with a target antigen, said first antigen corresponding to the target antigen and said second antigen corresponding to a modified form of the target antigen, wherein the rate of intracellular proteolytic degradation of the second antigen is increased, enhanced or otherwise elevated relative to the first antigen.

In yet another aspect, the invention extends to the use of a first antigen or a polynucleotide from which the first antigen is expressible, together with antigen-presenting cells, in the preparation of a medicament for the treatment of a disease or condition associated with a target antigen, wherein said first antigen corresponds to the target antigen and wherein said antigen-presenting cells have been exposed to a second antigen, corresponding to a modified form of the target antigen, whose rate of intracellular proteolytic degradation is increased, enhanced or otherwise elevated relative to the first antigen, for a time and under conditions sufficient to express a processed form of said second antigen for presentation to, and modulation of, T cells.

In still yet another aspect, the invention contemplates the use of a antigen-presenting cells in the preparation of a medicament for the treatment of a disease or condition associated with a target antigen, wherein said antigen-presenting cells have been exposed to a first antigen corresponding to the target antigen, or to a polynucleotide from which the first antigen is expressible, together with a second antigen, corresponding to a modified form of the target antigen, whose rate of intracellular proteolytic degradation is increased, enhanced or otherwise elevated relative to the first antigen, or to a polynucleotide from which the second antigen is expressible, for a time and under conditions sufficient to express a processed form of said first antigen and a processed form of said second antigen for presentation to, and modulation of, T cells.

The invention also encompasses the use of the synthetic polypeptide, the synthetic polynucleotide and the synthetic construct as broadly described above in the study, and modulation of immune responses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical representation showing immunogenicity of codon-modified and unmodified HPV 6L1. Graphs a and b show reactivity of sera from mice immunised with (▪) codon-modified L1 pH6L1Δ, single immunisation, or (▾) codon-modified L1 (pH6L1Δ), double imnmunisation, or (●) codon-unmodified L1(p6L1Δ), double immunisation with (a) HPV6bL1 VLPs (conformational antibody) or (b) denatured HPV6b L1 (linear antibody); Graphs c and d show reactivity of sera from mice immunised with (▪) codon-modified HPV6b L1E7.1, (▴) codon modified HPV6b L1-E7.2, (♦) codon-modified HPV6b L1-HPV16E7 or (▾) native sequence HPV6b L1 with (c) HPV6b L1 VLPs (conformational antibody), or (d) denatured HPV6b L1 (linear antibody). All results are means±1S.E.M from groups of 5 mice. Graph e shows reactivity of sera from mice immunised with p6HL116E7(▪▴), ubiquitin-conjugated pU6HL116E7(▾♦) or pCDNA3 (●□) against native VLPs (▪▾●) or denatured L1 (▴♦□). Graph f shows serum reactivity to recombinant HPV6b E7 from mice immunised with (lane 1,4) pH6L1E7.1, (lane 2,5) pH6L1E7.2, or (lane 3,6) p6L1Δ. Lane 1-3: lysate from Cos-1 cells transfected with pCDNAE7. Lane 4-6: Cos-1 cell lysate.

FIG. 2 is a graphical representation showing cell-mediated immunity to L1 induced by polynucleotide vaccines. Graph a shows cutaneous DTH responses to L1 measured in groups of mice immunised with codon-modified pH6L1Δ, or codon-modified chimeric H6L1E7.1 or 0.2, with unmodified p6L1 or p6L1Δ, or with pCDNA3 vector. Graph b illustrates HPV 16 E7 CTL epitope specific IFNγ secreting lymph node T cell precursors in C57BL/6 mice immunised with either pcDNA3, codon-modified HPV6L1-HPV16E7 (pH6L1E7) or ubiquitin-conjugated codon-modified HPV6L1-HPV16E7 DNA (pUH6L1E7). Mean of triplicates±1 SD are shown. Graph c shows protection against the subcutaneous growth of E7 expressing TC-1 tumours in mice immunised with pcDNA3, pH6L116E7 paired t test, P<0.01, pH6L116E7 vs pUH6L116E7), or pUH6L116E7 DNA (paired t test, P<0.01, pcDNA3 vs pUH6L116E7).

FIG. 3 is a graphical representation illustrating induction of neutralising antibody and CD8+ve T cells by a mixed polynucleotide vaccine comprising ubiquitin conjugated and non conjugated HPV6bL116E7. a. HPV 16 E7 CTL epitope specific IFNγ secreting lymph node(L) or spleen(S) T cell precursors in C57BL/6 mice immunised with a mixture of codon modified HPV6L1-HPV16E7 and Ubiquitin conjugated codon modified HPV6L1-HPV16E7 DNA (mix) or a control

FIG. 4 is a photographic representation of a plate showing inhibition of HPV6 L1 induced agglutination of mouse erythiocytes by sera from mice immunised with codon-modified or unmodified HPV6b L1 DNA. Serial dilutions (1:100-1:12800) of sera from mice immunised with codon modified L1 genes; A: pH6L1A, one immunisation; B: pH6L1Δ, two immunisations; C: pH6L1E7.1; D: pH6L1E7.2, inhibited agglutination, whereas unmodified gene (E: p6L1Δ) did not induce inhibitory antibody. Rabbit anti-HPV6 L1 antibody (F) was used as a positive control.

FIG. 5 is a graphical representation showing immunogenicity of codon modified and unmodified BPV1 L2. Groups of C57BL/6 mice were immunised with HBL2E7(▪); HBL2(▴); L2E7(▾); L2(♦) and L2 specific reactivity measured by ELISA. Results are shown as the mean reactivity±1 SD.

BRIEF DESCRIPTION OF THE SEQUENCES Summary Table

TABLE A SEQUENCE ID DESCRIPTION LENGTH SEQ ID NO: 1 Human ubiquitin coding sequence (CDS), 1 copy 231 nts SEQ ID NO: 2 Polypeptide encoded by SEQ ID NO: 1 76 aa SEQ ID NO: 3 HPV type 6b wild-type L1 protein (L1) CDS as set forth 1503 nts in GenBank Accession No. NC_001355 SEQ ID NO: 4 Polypeptide encoded by SEQ ID NO: 3 500 aa SEQ ID NO: 5 Synthetic construct HPV type 6b humanised L1 protein 1503 nts (L1) CDS as set forth in GenBank Accession No. AF322411 SEQ ID NO: 6 Polypeptide encoded by SEQ ID NO: 5 500 aa SEQ ID NO: 7 Synthetic construct HPV type 6b wild-type truncated L1 1404 nts protein (L1) CDS SEQ ID NO: 8 Polypeptide encoded by SEQ ID NO: 7 467 aa SEQ ID NO: 9 Synthetic construct HPV type 6b humanised truncated 1404 nts L1 protein (L1) CDS as set forth in GenBank Accession No. AF322412 SEQ ID NO: 10 Polypeptide encoded by SEQ ID NO: 9 467 aa SEQ ID NO: 11 Synthetic construct HPV type 6b humanised L1/E7.1 1554 nts hybrid protein CDS as set forth in GenBank Accession No. AF322413 SEQ ID NO: 12 Polypeptide encoded by SEQ ID NO: 11 517 aa SEQ ID NO: 13 Synthetic construct HPV type 6b humanised L1/E7.2 1554 nts hybrid protein CDS as set forth in GenBank Accession No. AF322414 SEQ ID NO: 14 Polypeptide encoded by SEQ ID NO: 13 517 aa SEQ ID NO: 15 Synthetic construct HPV type 6b humanised 1728 nts L1/ubiqutin hybrid protein CDS as set forth in GenBank Accession No. AF322415 SEQ ID NO: 16 Polypeptide encoded by SEQ ID NO: 15 575 aa SEQ ID NO: 17 Synthetic construct HPV type 6b humanised 1677 nts ubiquitin/L1 delta/H-2 Db CTL epitope hybrid protein CDS as set forth in GenBank Accession No. AF323508 SEQ ID NO: 18 Polypeptide encoded by SEQ ID NO: 17 558 aa SEQ ID NO: 19 Synthetic construct HPV type 6b humanised L1 delta/H- 1452 nts 2 Db CTL CTL epitope hybrid protein CDS as set forth in GenBank Accession No. AF323509 SEQ ID NO: 20 Polypeptide encoded by SEQ ID NO: 19 483 aa SEQ ID NO: 21 BPV type 1 wild-type L2 protein (L2) CDS as set forth 1404 nts in GenBank Accession No. X01768 SEQ ID NO: 22 Polypeptide encoded by SEQ ID NO: 21 467 aa SEQ ID NO: 23 Synthetic construct BPV type 1 humanised L2 protein 1410 nts (L2) CDS SEQ ID NO: 24 Polypeptide encoded by SEQ ID NO: 23 469 aa

DETAILED DESCRIPTION OF THE INVENTION

1. Definitions

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, preferred methods and materials are described. For the purposes of the present invention, the following terms are defined below.

The articles “a” and “an” are used herein to refer to one or to more than one (i.e. to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element.

The term “about” is used herein to refer to conditions (e.g., amounts, concentrations, time etc) that vary by as much as 30%, preferably by as much as 20%, and more preferably by as much as 10% to a specified condition.

The terms “administration concurrently” or “administering concurrently” or “coadministering” and the like refer to the administration of a single composition containing two or more actives, or the administration of each active as separate compositions and/or delivered by separate routes either simultaneously or sequentially within a short enough period of time that the effective result is equivalent to that obtained when all such actives are administered as a single composition.

By “antigen-binding molecule” is meant a molecule that has binding affinity for a target antigen. It will be understood that this term extends to immunoglobulins, inununoglobulin fragments and non-immunoglobulin derived protein frameworks that exhibit antigen-binding activity.

By “autologous” is meant something (e.g., cells, tissues etc) derived from the same organism.

The term “allogeneic” as used herein refers to cells, tissues, organisms etc that are of different genetic constitution although derived from the same species.

By “biologically active fragment” is meant a fragment of a full-length parent polypeptide which fragment retains the activity of the parent polypeptide. For example, a biologically active fragment of ubiquitin when conjugated to an antigen of interest will increase, enhance or otherwise elevate the rate of intracellular proteolytic degradation of that antigen. As used herein, the term “biologically active fragment” includes deletion mutants and small peptides, for example of at least 8, preferably at least 10, more preferably at least 15, even more preferably at least 20 and even more preferably at least 30 contiguous amino acids, which comprise the above activity. Peptides of this type may be obtained through the application of standard recombinant nucleic acid techniques or synthesised using conventional liquid or solid phase synthesis techniques. For example, reference may be made to solution synthesis or solid phase synthesis as described, for example, in Chapter 9 entitled “Peptide Synthesis” by Atherton and Shephard which is included in a publication entitled “Synthetic Vaccines” edited by Nicholson and published by Blackwell Scientific Publications. Alternatively, peptides can be produced by digestion of a polypeptide of the invention with proteinases such as endoLys-C, endoArg-C, endoGlu-C and staphylococcus V8-protease. The digested fragments can be purified by, for example, high performance liquid chromatographic (HPLC) techniques.

As used herein, the term “cis-acting sequence” or “cis-regulatory region” or similar term shall be taken to mean any sequence of nucleotides which is derived from an expressible genetic sequence wherein the expression of the genetic sequence is regulated, at least in part, by said sequence of nucleotides. Those skilled in the art will be aware that a cis-regulatory region may be capable of activating, silencing, enhancing, repressing or otherwise altering the level of expression and/or cell-type-specificity and/or developmental specificity of any structural gene sequence.

Throughout this specification, unless the context requires otherwise, the words “comprise”, “comprises” and “comprising” will be understood to imply the inclusion of a stated step or element or group of steps or elements but not the exclusion of any other step or element or group of steps or elements.

By “corresponds to” or “corresponding to” is meant a polynucleotide (a) having a nucleotide sequence that is substantially identical or complementary to all or a portion of a reference polynucleotide sequence or (b) encoding an amino acid sequence identical to an amino acid sequence in a peptide or protein. This phrase also includes within its scope a peptide or polypeptide having an amino acid sequence that is substantially identical to a sequence of amino acids in a reference peptide or protein.

By “derivative” is meant a polypeptide that has been derived from the basic sequence by modification, for example by conjugation or complexing with other chemical moieties or by post-translational modification techniques as would be understood in the art. The term “derivative” also includes within its scope alterations that have been made to a parent sequence including additions, or deletions that provide for functionally equivalent molecules.

By “effective amount”, in the context of treating, preventing or ameliorating the symptoms of a condition, is meant the administration of that amount of immunopotentiating composition or active compound that elicits an immune response in an individual in need of such treatment, prevention or amelioration, either in a single dose or as part of a series, that is effective for treatment of that condition. The effective amount will vary depending upon the health and physical condition of the individual to be treated, the taxonomic group of individual to be treated, the formulation of the composition, the assessment of the medical situation, and other relevant factors. It is expected that the amount will fall in a relatively broad range that can be determined through routine trials.

By “expressing”, and like terms such as “expression” and “expressible”, in the context or protein expression, is meant expression of a protein to a level sufficient to effect a particular fimction associated with the protein.

By “expressing said polynucleotide” is meant transcribing the polynucleotide such that mRNA is produced.

By “expression vector” is meant any autonomous genetic element capable of directing the synthesis of a protein encoded by the vector. Such expression vectors are known by practitioners in the art.

The term “gene” is used in its broadest context to include both a genornic DNA region corresponding to the gene as well as a cDNA sequence corresponding to exons or a recombinant molecule engineered to encode a functional form of a product.

“Homology” refers to the percentage number of amino acids that are identical or constitute conservative substitutions as defined in Table B infra. Homology may be determined using sequence comparison programs such as GAP (Deveraux et al. 1984). In this way, sequences of a similar or substantially different length to those cited herein might be compared by insertion of gaps into the alignment, such gaps being determined, for example, by the comparison algorithm used by GAP.

To enhance immune response (“immunoenhancement”), as is well-known in the art, means to increase the animal's capacity to respond to foreign or disease-specific antigens (e.g., viral antigens, cancer antigens) i.e., those cells primed to attack such antigens are increased in number, activity, and ability to detect and destroy those antigens. Strength of immune response is measured by standard tests including: direct measurement of peripheral blood lymphocytes by means known to the art; natural killer cell cytotoxicity assays (see, e.g., Provinciali et al. (1992, J. Immunol. Meth. 155: 19-24), cell proliferation assays (see, e.g., Vollenweider and Groseurth (1992, J. Immunol. Meth. 149: 133-135), immunoassays of immune cells and subsets (see, e.g., Loeffler et al. (1992, Cytom. 13: 169-174); Rivoltini et al. (1992, Can. Immunol. Immunother. 34: 241-251); or skin tests for cell-mediated immunity (see, e.g., Chang et al. (1993, Cancer Res. 53: 1043-1050). Any statistically significant increase in strength of immune response as measured by the foregoing tests is considered “enhanced immune response” “immunoenhancement” or “immunopotentiation” as used herein. Enhanced immune response is also indicated by physical manifestations such as fever and inflammation, as well as healing of systemic and local infections, and reduction of symptoms in disease, i.e., decrease in tumour size, alleviation of symptoms of a disease or condition including, but not restricted to, leprosy, tuberculosis, malaria, naphthous ulcers, herpetic and papillomatous warts, gingivitis, artherosclerosis, the concomitants of AIDS such as Kaposi's sarcoma, bronchial infections, and the like. Such physical manifestations also define “enhanced immune response” “inmunoenhancement” or “immunopotentiation” as used herein.

Reference herein to “immuno-interactive” includes reference to any interaction, reaction, or other form of association between molecules and in particular where one of the molecules is, or mimics, a component of the immune system.

By “isolated” is meant material that is substantially or essentially free from components that normally accompany it in its native state.

By “modulating” is meant increasing or decreasing, either directly or indirectly, the level and/or functional activity of a target molecule. For example, an agent may indirectly modulate the said level/activity by interacting with a molecule other than the target molecule. In this regard, indirect modulation of a gene encoding a target polypeptide includes within its scope modulation of the expression of a first nucleic acid molecule, wherein an expression product of the first nucleic acid molecule modulates the expression of a nucleic acid molecule encoding the target polypeptide.

The term “5′ non-coding region” is used herein in its broadest context to include all nucleotide sequences which are derived from the upstream region of an expressible gene, other than those sequences which encode amino acid residues which comprise the polypeptide product of said gene, wherein 5′ non-coding region confers or activates or otherwise facilitates, at least in part, expression of the gene.

The term “oligonucleotide” as used herein refers to a polymer composed of a multiplicity of nucleotide units (deoxyribonucleotides or ribonucleotides, or related structural variants or synthetic analogues thereof) linked via phosphodiester bonds (or related structural variants or synthetic analogues thereof). Thus, while the term “oligonucleotide” typically refers to a nucleotide polymer in which the nucleotides and linkages between them are naturally occurring, it will be understood that the term also includes within its scope various analogues including, but not restricted to, peptide nucleic acids (PNAs), phosphoramidates, phosphorothioates, methyl phosphonates, 2-O-methyl ribonucleic acids, and the like. The exact size of the molecule may vary depending on the particular application. An oligonucleotide is typically rather short in length, generally from about 10 to 30 nucleotides, but the term can refer to molecules of any length, although the term “polynucleotide” or “nucleic acid” is typically used for large oligonucleotides.

The term “operably connected” or “operably linked” as used herein means placing a structural gene under the regulatory control of a promoter, which then controls the transcription and optionally translation of the gene. In the construction of heterologous promoter/structural gene combinations, it is generally preferred to position the genetic sequence or promoter at a distance from the gene transcription start site that is approximately the same as the distance between that genetic sequence or promoter and the gene it controls in its natural setting; i.e. the gene from which the genetic sequence or promoter is derived. As is known in the art, some variation in this distance can be accommodated without loss of function. Similarly, the preferred positioning of a regulatory sequence element with respect to a heterologous gene to be placed under its control is defined by the positioning of the element in its natural setting; i.e. the genes from which it is derived.

The term “patient” refers to patients of human or other mammal and includes any individual it is desired to examine or treat using the methods of the invention. However, it will be understood that “patient” does not imply that symptoms are present. Suitable mammals that fall within the scope of the invention include, but are not restricted to, primates, livestock animals (e.g., sheep, cows, horses, donkeys, pigs), laboratory test animals (e.g., rabbits, mice, rats, guinea pigs, hamsters), companion animals (e.g., cats, dogs) and captive wild animals (e.g., foxes, deer, dingoes).

By “pharmaceutically-acceptable carrier” is meant a solid or liquid filler, diluent or encapsulating substance that may be safely used in topical or systemic administration.

The term “polynucleotide” or “nucleic acid” as used herein designates mRNA, RNA, cRNA, cDNA or DNA. The term typically refers to oligonucleotides greater than 30 nucleotides in length.

“Polypeptide”, “peptide” and “protein” are used interchangeably herein to refer to a polymer of amino acid residues and to variants and synthetic analogues of the same. Thus, these terms apply to amino acid polymers in which one or more amino acid residues is a synthetic non-naturally occurring amino acid, such as a chemical analogue of a corresponding naturally occurring amino acid, as well as to naturally-occurring amino acid polymers.

By “primer” is meant an oligonucleotide which, when paired with a strand of DNA, is capable of initiating the synthesis of a primer extension product in the presence of a suitable polymerising agent. The primer is preferably single-stranded for maximum efficiency in amplification but may alternatively be double-stranded. A primer must be sufficiently long to prime the synthesis of extension products in the presence of the polymerisation agent. The length of the primer depends on many factors, including application, temperature to be employed, template reaction conditions, other reagents, and source of primers. For example, depending on the complexity of the target sequence, the oligonucleotide primer typically contains 15 to 35 or more nucleotides, although it may contain fewer nucleotides. Primers can be large polynucleotides, such as from about 200 nucleotides to several kilobases or more. Primers may be selected to be “substantially complementary” to the sequence on the template to which it is designed to hybridise and serve as a site for the initiation of synthesis. By “substantially complementary”, it is meant that the primer is sufficiently complementary to hybridise with a target nucleotide sequence. Preferably, the primer contains no mismatches with the template to which it is designed to hybridise but this is not essential. For example, non-complementary nucleotides may be attached to the 5′ end of the primer, with the remainder of the primer sequence being complementary to the template. Alternatively, non-complementary nucleotides or a stretch of non-complementary nucleotides can be interspersed into a primer, provided that the primer sequence has sufficient complementarity with the sequence of the template to hybridise therewith and thereby form a template for synthesis of the extension product of the primer.

“Probe” refers to a molecule that binds to a specific sequence or sub-sequence or other moiety of another molecule. Unless otherwise indicated, the term “probe” typically refers to a polynucleotide probe that binds to another nucleic acid, often called the “target nucleic acid”, through complementary base pairing. Probes may bind target nucleic acids lacking complete sequence complementarity with the probe, depending on the stringency of the hybridisation conditions. Probes can be labelled directly or indirectly.

Reference herein to a “promoter” is to be taken in its broadest context and includes the transcriptional regulatory sequences of a classical genomic gene, including the TATA box which is required for accurate transcription initiation, with or without a CCAAT box sequence and additional regulatory elements (i.e. upstream activating sequences, enhancers and silencers) which alter gene expression in response to developmental and/or environmental stimuli, or in a tissue-specific or cell-type-specific manner. A promoter is usually, but not necessarily, positioned upstream or 5′, of a structural gene, the expression of which it regulates. Furthermore, the regulatory elements comprising a promoter are usually positioned within 2 kb of the start site of transcription of the gene. Preferred promoters according to the invention may contain additional copies of one or more specific regulatory elements to further enhance expression in a cell, and/or to alter the timing of expression of a structural gene to which it is operably connected.

The term “recombinant polynucleotide” as used herein refers to a polynucleotide formed in vitro by the manipulation of nucleic acid into a form not normally found in nature. For example, the recombinant polynucleotide may be in the form of an expression vector. Generally, such expression vectors include transcriptional and translational regulatory nucleic acid operably linked to the nucleotide sequence.

By “recombinant polypeptide” is meant a polypeptide made using recombinant techniques, i.e., through the expression of a recombinant polynucleotide.

The term “synonymous codon” as used herein refers to a codon having a different nucleotide sequence than another codon but encoding the same amino acid as that other codon.

By “translational efficiency”, is meant the efficiency of a cell's protein synthesis machinery to incorporate the amino acid encoded by a codon into a nascent polypeptide chain. This efficiency can be evidenced, for example, by the rate at which the cell is able to synthesise the polypeptide from an RNA template comprising the codon, or by the amount of the polypeptide synthesised from such a template.

By “vector” is meant a nucleic acid molecule, preferably a DNA molecule derived, for example, from a plasmid, bacteriophage, or plant virus, into which a nucleic acid sequence may be inserted or cloned. A vector preferably contains one or more unique restriction sites and may be capable of autonomous replication in a defined host cell including a target cell or tissue or a progenitor cell or tissue thereof, or be integrable with the genome of the defined host such that the cloned sequence is reproducible. Accordingly, the vector may be an autonomously replicating vector, i.e., a vector that exists as an extrachromosomal entity, the replication of which is independent of chromosomal replication, e.g., a linear or closed circular plasmid, an extrachromosomal element, a minichromosome, or an artificial chromosome. The vector may contain any means for assuring self-replication. Alternatively, the vector may be one which, when introduced into the host cell, is integrated into the genome and replicated together with the chromosome(s) into which it has been integrated. A vector system may comprise a single vector or plasmid, two or more vectors or plasmids, which together contain the total DNA to be introduced into the genome of the host cell, or a transposon. The choice of the vector will typically depend on the compatibility of the vector with the host cell into which the vector is to be introduced. The vector may also include a selection marker such as an antibiotic resistance gene that can be used for selection of suitable transformants. Examples of such resistance genes are well known to those of skill in the art.

2. Abbreviations

BPV: Bovine papillomavirus

CRPV: Cottontail rabbit papillomavirus

DTH: Delayed Type Hypersensitivity

HAI: hemagglutination inhibition assay

HPV: Human papillomavirus

PV: papillomavirus

VLP: virus like particle

3. Production of Antigens of the Invention

In work leading up to the present invention, the inventors sought to develop immunogenic agents, particularly polynucleotides, which would combine the desired effects of enhanced immunogenicity, as well as predictable/controlled ability to elicit host-protective antibody, whilst not precluding or diminishing the induction of a cell-mediated response to facilitate treatment of existing infection. It was observed that in cases where antibody was favoured, the approach used reduced the induction of a cell-mediated response. Similarly, in cases where the latter effect was favoured, the approach used reduced the former desired effect. In seeking to overcome one of the difficulties without removing the second desired benefit, the inventors inadvertently discovered that by tackling simultaneously the problems of impaired immunogenicity and controlled immunological responses, a combined approach could overcome both hurdles.

Accordingly, the present invention is predicated in part on a novel strategy for eliciting simultaneously a host-protective antibody response and a cell-mediated immune response against a target antigen to combat, inter alia, conditions that have latency periods and, therefore, benefit from the dual approach of prophylaxis and therapy. The strategy involves administering to an individual a first antigen corresponding to the target antigen, and being suitably intracellularly resistant to proteolysis. In addition, a second antigen, corresponding to a modified form of the target antigen, is administered to the individual, wherein the rate of intracellular proteolytic degradation of the second antigen is increased, enhanced or otherwise elevated relative to the first antigen. The first and second antigens may be administered in proteinaceous form, or in nucleic acid form, or a combination thereof. The antigenic determinant(s) or epitope(s) of the first antigen and the second antigen may be the same or different. Accordingly, the epitope-containing sequence of the first antigen and the second antigen may be the same or different. Preferably, the first antigen and the second antigen comprise the same epitope(s). Suitably, when corresponding epitopes are different between the first antigen and the second antigen, such epitopes are preferably capable of eliciting the production of elements that bind to a corresponding epitope of the target antigen.

Exemplary target antigens include, but are not limited to, at least a portion of a structural protein including, but not restricted to, structural proteins of pathogenic organisms (e.g., viral, bacterial, fungal, protozoan) such as capsid proteins or capsomers. In a preferred embodiment, the capsid protein is of viral origin. Preferably, the viral capsid protein relates to a crystalline virus. Examples of suitable viral capsid proteins include, but are not restricted to, the L1 and/or L2 proteins of papillomavirus, the capsid proteins of a Herpesvirus (e.g., GpD and GpB), VP1-3 of polyomavirus, VP1-6 of blue tongue virus, Hepatitis B surface antigen, Hepatitis C surface antigen, the capsid proteins of Parvovirus, the capsid proteins of Yeast Ty particles, the capsid proteins of Retroviruses (e.g., HIV and RSV), the capsid proteins of Rotavirus, the capsid proteins of Coronaviruses, and the capsid proteins of Adenovirns. Alternatively, the target antigen is a structural protein relating to the crystalline core of a lipid enveloped virus. For a more comprehensive list of viral structural proteins, see Fields Virology (editors-in-chief, Bernard N. Fields, David M. Knipe, Peter M. Howley, 4^(th) edition, Lippincott-Raven Publishers, 1999, Philadelphia, USA).

Alternatively, suitable viral capsid proteins include those that can be used to produce virus-like particles including, but not restricted to, Ty-virus-like particles as for example described by Oliveira-Ferreira et al. (2000 Vaccine, 18 (17): 1863-1869), Hirschberg et al. (1999, Int Immunol, 11 (12): 1927-1934), Klein et al. (1997, AIDS Res Hum Retroviruses, 13(5): 393-399), Allsopp et al. (1996, Eur J. Immunol, 26 (8): 1951-195), Bachmann et al. (1996, supra), Layton et al. (1996, Immunology, 87 (2): 171-178; 1993, J Immunol, 151 (2): 1097-1107), Brookman et al. (1995, Virology, 207 (1): 59-67), Burns et al. (1994, Mol Biotechnol, 1 (2): 137-145), Martin et al. (1993, AIDS, 7(10): 1315-1323) and Adams et al. (1987, Nature, 329 (6134): 68-70), human immuno deficiency virus-like particles as for example described by Paliard et al. (2000, AIDS Res Hum Retroviruses, 16 (3): 273-282), Notka et al. (1999, Biol Chem, 380 (3): 341-352) and Wagner et al. (1998, Virology, 245 (1): 65-74; 1994, Behring Inst Mitt, (95): 23-34), Norwalk virus-like particles as for example described by Ball et al. (1999, Gastroenterology, 117 (1): 40-48) and White et al. (1996, J Virol, 70 (10): 6589-6597), p24-VLP as for example described by Benson et al. (1999, AIDS Res Hum Retroviruses, 15 (2): 105-113), papilloma virus-like particles as for example described by Zhou et al. (1991, Virology, 181: 203-210; ibid 185: 251-257; and International publication WO 93/02184), Christensen et al. (2000, Virology, 269 (2): 451-461), and Benyacoub et al., (1999, Infect Immun, 67 (7): 3674-3679), Hepatitis virus-like particles as for example described by Falcon et al. (1999, Tissue Cell, 31 (2): 117-125), L1 et al. (1997, J Virol, 71 (10): 7207-7213) and Schirmbeck et al. (1996, Intervirology, 39 (1-2): 111-119), polyomavirus virus-like particles as for example described by Goldmann et al. (1999, J Virol, 73 (5): 4465-4469) and Szomolanyi-Tsuda et al, (1998, J Virol, 72 (8): 6665-6670), adeno-associated virus-like particles as for example described by Hoque et al. (1999, Biochem Biophys Res Commun, 266 (2): 371-376), infectious bursal disease virus-like particles as for example described by Hu et al. (1999 Biotechnol Bioeng, 63 (6): 721-729), Kibenge et al. (1999, Can J. Vet Res, 63 (1): 49-55) and Fernandez-Arias et al. (1998, J Gen Virol, 79 (Pt 5): 1047-1054), rotavirus-like particles as for example described by Jiang et al. (1999, Vaccine, 17 (7-8): 1005-1013), Ciarlet et al (1998, J Virol, 72 (11): 9233-9246), Gilbert et al. (1997, J Virol, 71 (6): 4555-4563) and Conner et al. (1996, J Infect Dis, 174 Suppl 1:S88-S92), calicivirus-like particles as for example described by Jiang et al. (1999, J Virol Methods, 78 (1-2): 81-91), bovine leukemia virus-like particles as for example described by Kakker et al. (1999, Virology, 265 (2): 308-318), rabbit haemorrhagic disease virus-like particles as for example described by Nagesha et al. (1999, Arch Virol, 144 (12): 2429-2439), parvovirus-like particles as for example described by Sedlik et al. (1999, J Virol, 73 (4): 2739-2744), Lo-Man et al. (1998, Eur J Immunol, 28 (4): 1401-1407) and Sedlik et al. (1997, Proc Natl Acad Sci USA, 94 (14): 7503-7508, transposable element D-based virus like particles as for example described by Hajek et al. (1998, J Virol, 72 (11): 8718-8724), mouse coronavirus-like particles as for example described by Bos et al. (1997, J Virol, 71 (12): 9427-9433; 1996, Virology, 218 (1): 52-60), potato leafroll luteovirus-like particles as for example described by Lamb et al. (1996, J Gen Virol, 77 (Pt 7): 1349-1358), bluetongue virus-like particles as for example described by Murray and Eaton. (1996, Vaccines for. Aust Vet J, 73 (6): 207-210), protozoan virus-like particles as for example described by Sita-Bobadilla et al. (1996, Int J Parasitol, 26 (4): 457-459), and Epstein-Barr virus-like particles as for example described by Yano et al. (1986, Int J. Cancer, 38 (2): 275-284). In a preferred embodiment, the capsid protein is a papillomavirus capsid protein. The capsid protein is suitably selected from L1 and L2 capsid proteins.

3.1 Production of Modified Antigen

A second or modified antigen according to the present invention may be prepared using any suitable technique that renders it less resistant to proteolysis intracellularly relative to a first antigen corresponding to the target antigen of interest. However, it should be noted that the present invention is not dependent on, and not directed to, any one particular technique by which the second or modified antigen is produced. The intracellular half life of a first or target antigen is suitably greater than about 3 minutes, preferably greater than about 5 minutes, more preferably greater than about 10 minutes, even more preferably greater than about 15 minutes, even more preferably greater than about 30 minutes, even more preferably greater than about 1 hour, even more preferably greater than about 10 hours, even more preferably greater than about 24 hours, and still even more preferably greater than about 50 hours. Suitably, a proteolytically resistant antigen is one that retains greater than about 10% of its tertiary structure after about 3 minutes, preferably after about 5 minutes, more preferably after about 10 minutes, even more preferably after about 15 minutes, even more preferably after about 30 minutes, even more preferably after about 1 hour, even more preferably after about 10 hours, even more preferably after about 24 hours, and still even more preferably after about 50 hours at intracellular or intracellular-like conditions. Preferably, a proteolytically resistant antigen is one that retains greater than about 20% of its tertiary structure after about 3 minutes, preferably after about 5 minutes, more preferably after about 10 minutes, even more preferably after about 15 minutes, even more preferably after about 30 minutes, even more preferably after about 1 hour, even more preferably after about 10 hours, even more preferably after about 24 hours, and still even more preferably after about 50 hours at intracellular or intracellular-like conditions. More preferably, a proteolytically resistant antigen is one that retains greater than about 50% of its tertiary structure after about 3 minutes, preferably after about 5 minutes, more preferably after about 10 minutes, even more preferably after about 15 minutes, even more preferably after about 30 minutes, even more preferably after about 1 hour, even more preferably after about 10 hours, even more preferably after about 24 hours, and still even more preferably after about 50 hours at intracellular or intracellular-like conditions. The intracellular or intracellular-like conditions are preferably physiological for the cell type. The cell type is preferably an antigen presenting cell, more preferably a professional antigen presenting cell including, but not restricted to, a dendritic cell, a macrophage and a B cell. The temperature of the intracellular or intracellular-like conditions is preferably physiological for the cell type. Exemplary temperatures for mammalian cells range suitably from about 30° C. to about 42° C., and preferably from about 35° C. to about 37° C. The intracellular half life of the second antigen is suitably less than about 50 hours, preferably less than about 10 hours, more preferably less than about 1 hour, even more preferably less than about 30 minutes, even more preferably less than about 15 minutes, even more preferably less than about 10 minutes and still even more preferably less than about 3 minutes. At a minimum, enhanced proteolytic degradation of the second antigen refers to a level of proteolytic degradation that is at least about 5%, preferably at least about 10%, more preferably at least about 20%, even more preferably at least about 40%, even more preferably at least about 50%, even more preferably at least about 60%, even more preferably at least about 70%, even more preferably at least about 80%, even more preferably at least about 90%, sill even more preferably at least about 95%, greater than that of the target or first antigen. Assays for measuring degradation of proteins are known to persons of skill in the art. For example, proteolytic degradation may be measured using a mammalian cell lysate assay including, but not restricted to, the reticulocyte lysate assay of Bachmair et al in U.S. Pat. No. 5,646,017.

The second antigen may be derived from a parent antigen corresponding to the target antigen. The parent antigen is suitably selected from a natural antigen, a synthetic antigen or a combination thereof. Preferably, the parent antigen is modified to include an intracellular degradation signal or degron. The degron is suitably a ubiquitin-mediated degradation signal selected from a destabilising amino acid at the amino-terminus of an antigen, a ubiquitin acceptor, a ubiquitin or combination thereof.

Thus, in one embodiment, the parent antigen is modified to include a destabilising amino acid at its amino-terminus so that the protein so modified is subject to the N-end rule pathway as disclosed, for example, by Bacbmair et al in U.S. Pat. No. 5,093,242 and by Varshavsky et al. in U.S. Pat. No. 5,122,463. In a preferred embodiment of this type, the destabilising amino acid is selected from isoleucine and glutamic acid, more preferably from histidine tyrosine and glutamine, and even more preferably from aspartic acid, asparagine, phenylalanine, leucine, tryptophan and lysine. In an especially preferred embodiment, the destabilising amino acid is arginine. In some proteins, the amino-terminal end is obscured as a result of the protein's conformation (i.e., its tertiary or quaternary structure). In these cases, more extensive alteration of the amino-terminus may be necessary to make the protein subject to the N-end rule pathway. For example, where simple addition or replacement of the single amino-terminal residue is insufficient because of an inaccessible amino-terminus, several amino acids (including lysine, the site of ubiquitin joining to substrate proteins) may be added to the original amino-terminus to increase the accessibility and/or segmental mobility of the engineered amino terminus.

Proteins can be designed or modified at the protein or nucleic acid level to provide a second antigen with the desired metabolic characteristics. A straightforward approach to modifying a parent protein in order to increase its metabolic stability is to directly engineer the amino-terminus of the protein at the protein level. To provide a desired amino-terminal amino acid, the amino-terminus of the protein of interest can be chemically altered, for example, by adding an amino acid of the destabilising class to the amino-terminus of a protein or polypeptide, employing an appropriate chemistry. Thus, for example, a stable protein can be destabilised by adding a destabilising amino acid to the amino-terminus. One distinct way to modify the amino-terminus of a protein would be to employ specific enzymes, amino acid-protein ligases, which catalyse post-translational addition of a single amino acid to the protein's amino-terminus. Other methods for non-genetic alterations of the same type can readily be ascertained by those skilled in the art.

Modification or design of the amino-terminus of a protein can also be accomplished at the genetic level. Conventional techniques of site-directed mutagenesis for addition or substitution of appropriate codons to the 5′ end of an isolated or synthesised antigen-encodinig polynucleotide can be employed to provide a desired amino-terminal structure for the encoded protein. For example, so that the protein expressed has the desired amino acid at its amino-terminus the appropriate codon for a destabilising amino acid can be inserted or built into the amino-terminus of the protein-encoding sequence. Where necessary, a nucleic acid sequence encoding the amino-terminal region of a protein can be modified to introduce one or more lysine residues in an appropriate context, which act as a ubiquitin acceptor as described in more detail below. This can be achieved most conveniently by employing DNA constructs encoding “universal destabilising segments”. A universal destabilising segment comprises a nucleic acid construct which encodes a polypeptide structure, preferably segmentally mobile, containing one or more lysine residues, the codons for lysine residues being positioned within the construct such that when the construct is inserted into the coding sequence of the antigen-encoding polynucleotide, the lysine residues are sufficiently spatially proximate to the amino-terminus of the encoded protein to serve as the second determinant of the complete amino-terminal degradation signal. The insertion of such constructs into the 5′ portion of a antigen-encoding polynucleotide would provide the encoded protein with a lysine residue (or residues) in an appropriate context for destabilisation.

The codon for the amino-terminal amino acid of the protein of interest can be made to encode the desired amino acid by, for example, site-directed mutagenesis techniques currently standard in the field. Suitable mutagenesis methods are described for example in the relevant sections of Ausubel, et al. (supra) and of Sambrook, et al., (supra). Alternatively, suitable methods for altering DNA are set forth, for example, in U.S. Pat. Nos. 4,184,917, 4,321,365 and 4,351,901, which are incorporated herein by reference. Instead of in vitro mutagenesis, the synthetic polynucleotide can be synthesised de novo using readily available machinery. Sequential synthesis of DNA is described, for example, in U.S. Pat. No. 4,293,652. However, it should be noted that the present invention is not dependent on, and not directed to, any one particular technique for constructing a polynucleotide encoding a modified antigen as described herein.

If the antigen-encoding polynucleotide is a synthetic or recombinant polynucleotide the appropriate 5′ codon can be built-in during the synthetic process. Alternatively, nucleotides for a specific codon can be added to the 5′ end of an isolated or synthesised polynucleotide by ligation of an appropriate nucleic acid sequence to the 5′ (amino-terminus-encoding) end of the polynucleotide. Nucleic acid inserts encoding appropriately located lysine residues (such as the “universal destabilising segments” described above) can suitably be inserted into the 5′ region to provide for the second determinant of the complete amino-terminal degradation.

In a preferred embodiment, the second or modified antigen, which comprises a destabilising amino acid at its amino terminus, is fused or otherwise conjugated to a. masking entity, which masks said amino terminus so that when unmasked the second antigen will exhibit the desired rate of intracellular proteolytic degradation. Suitably, the masking entity is a masking protein sequence. The fusion protein is designed so that the masking protein sequence fused to the amino-terminus of the protein of interest is susceptible to specific cleavage at the junction between the two. Removal of the protein sequence thus unmasks the amino-terminus of the protein of interest and the half-life of the released protein is thus governed by the predesigned amino-terminus. The fusion protein can be designed for specific cleavage in vivo, for example, by a host cell endoprotease or for specific cleavage in a in vitro system where it can be cleaved after isolation from a producer cell (which lacks the capability to cleave the fusion protein). Thus, in a preferred embodiment, the masking protein sequence is cleavable by an endoprotease, which is preferably an endogenous endoprotease of a mammalian cell. Suitable endoproteases include, but are not restricted to, serine endoproteases (e.g., subtilisins and furins) as described, for example, by Creemers, et al. (1998, Semin. Cell Dev. Biol. 9 (1): 3-10), proteasomal endopeptidases as described, for example, by Zwickl, et al. (2000, Curr. Opin. Struct. Biol. 10 (2): 242-250), proteases relating to the MHC class I processing pathway as described, for example, by Stolze et al. (2000, Nat. Immunol. 1 413-418) and signal peptidases as described, for example, by Dalbey, et al. (1997, Protein Sci. 6 (6): 1129-1138). In a preferred embodiment of this type, the masking protein sequence comprises a signal peptide sequence. Suitable signal peptides sequences are described, for example, by Nothwehr et al (1990, Bioessays 12 (10): 479-484), Izard, et al. (1994, Mol. Microbiol. 13 (5): 765-773), Menne, et al (2000, Bioinformatics. 16 (8): 741-742) and Ladunga (2000, Curr. Opin. Biotechnol. 11 (1): 13-18). Suitably, an endoprotease cleavage site is interposed between the masking protein sequence and the second antigen.

A second or modified antigen with an attached masking sequence may be conveniently prepared by fusing a nucleic acid sequence encoding a masking protein sequence upstream of another nucleic acid sequence encoding an antigen; which corresponds to the target antigen of interest and which includes a destabilising amino acid at its amino-terminus. The codon for the amino-terminal amino acid of the antigen of interest is suitably located immediately adjacent to the 3′ end of the masking protein-encoding nucleic acid sequence.

In another embodiment, the parent antigen is modified to include, or is otherwise associated with, an ubiquitin acceptor which is a molecule that preferably contains at least one residue appropriately positioned from the N-terminal of the antigen as to be able to be bound by ubiquitin molecules. Such residues preferentially have an epsilon amino group such as lysine. Physical analysis demonstrates that multiple lysine residues function as ubiquitin acceptor sites (King et al., 1996, Mol. Biol. Cell 7: 1343-1357; King et al, 1996, Science 274: 1652-1659). Examples of other ubiquitin acceptors include lacI or Sindis virus RNA polymerase. Ubiquitination at the N-terminal of the protein specifically targets the protein for degradation via the ubiquitin-proteosome pathway.

Other protein processing signals that destabilise an antigen of interest and allow for enhanced intracellular degradation are contemplated in the present invention. These other methods may not necessarily be mediated by the ubiquitin pathway, but may otherwise permit degradation of proteins in the cytoplasm via proteosomes. For example, the present invention contemplates the use of other intracellular processing signals which govern the rate(s) of intracellular protein degradation including, but not limited to, those described by Bohley et al. (1996, Biol. Chem. Hoppe. Seyler 377: 425-435). Such processing signals include those that allow for phosphorylation of the target protein (Yaglom et al., 1996, Mol. Cell Biol. 16: 3679-3684; Yaglom et al, 1995, Mol Cell Biol. 15: 731-741). Also contemplated by the present invention are modification of an parent antigen that allow for post-translational arginylation gerber et al 1987, Nature 326: 808-811; Bohley et al, 1991, Biomed. Biochim. Acta 50: 343-346) of the protein which can enhance its rate(s) of intracellular degradation. The present invention also contemplates the use of certain structural features of proteins that can influence higher rates of intracellular protein turn-over, including protein surface hydrophobicity, clusters of hydrophobic residues within the protein (Sadis et al, 1995, Mol. Cell Biol. 15: 4086-4094), certain hydrophobic pentapeptide motifs at the protein's carboxy-terminus (C-terminus) (e.g., ARINV (SEQ ID NO: 25), as found on the C-terminus of ornithine decarboxylase (Ghoda et al., 1992, Mol. Cell Biol. 12: 2178-2185; Li, et al., 1994, Mol. Cell Biol. 14: 87-92), or AANDENYALAA (SEQ ID NO: 26), as found in C-terminal tags of aberrant polypeptides (Keiler et al., 1996, Science 271: 990-993,) or PEST regions (regions rich in proline (P), glutamic acid (E), serine (S), and threonine (T), which are optionally flanked by amino acids comprising electropositive side chains Rogers et al. 1986, Science 234 (4774): 364-368; 1988, J. Biol. Chem. 263: 19833-19842). Moreover, certain motifs have been identified in proteins that appear necessary and possibly sufficient for achieving rapid intracellular degradation. Such motifs include RXALGXIXN (SEQ ID NO: 27) region (where X=any amino acid) in cyclins (Glotzer et al., 1991, Nature 349: 132-138) and the KTKRNYSARD (SEQ ID NO: 28) motif in isocitrate lyase (Ordiz et al., 1996, FEBS Lett. 385: 43-46).

The present invention also contemplates enhanced cellular degradation of a parent antigen which may occur by the incorporation into that antigen known protease cleavage sites. For example amyloid beta-protein can be cleaved by beta- and gamma-secretase (Iizuka et al. 1996, Biochem. Biophys. Res. Commun. 218: 238-242) and the two-chain vitamin K-dependent coagulation factor X can be cleaved by calcium-dependent endoprotease(s) in liver (Wallin et al, 1994, Thromb. Res. 73: 395-403).

In yet another embodiment, the parent antigen is conjugated to a ubiquitin or a biologically active fragment thereof, to produce a second or modified antigen whose rate of intracellular proteolytic degradation is increased, enhanced or otherwise elevated relative to the parent antigen. In a preferred embodiment of this type, the ubiquitin or biologically active fragment is fused, or otherwise conjugated, to the second antigen. Suitably, the ubiquitin is of mammalian origin, more preferably of human or other primate origin. In a preferred embodiment of this type, the ubiquitin comprises the sequence set forth in SEQ ID NO: 2. In an alternate embodiment, the ubiquitin comprises two or more copies the sequence set forth in SEQ ID NO: 2.

In one embodiment, the ubiquitin-antigen fusion protein is suitably produced by covalently attaching an antigen corresponding to the target antigen to a ubiquitin or a biologically active fragment thereof. Covalent attachment may be effected by any suitable means known to persons of skill in the art. For example, protein conjugates may be prepared by linking proteins together using bifunctional reagents. The bifunctional reagents can be homobifunctional or heterobifunctional.

Homobifunctional reagents are molecules with at least two identical functional groups. The functional groups of the reagent generally react with one of the functional groups on a protein, typically an amino group. Examples of homobifunctional reagents include glutaraldehyde and diimidates. An example of the use of glutaraldehyde as a cross-linking agent is described by Poznansky et al. (1984, Science, 223: 1304-1306). The use of diimidates as a cross-linking agent is described for example by Wang, et al. (1977, Biochemistry, 16: 2937-2941). Although it is possible to use homobifunctional reagents for the purpose of forming a modified antigen according to the invention, skilled practitioners in the art will appreciate that it is difficult to attach different proteins in an ordered fashion with these reagents. In this regard, in attempting to link a first protein with a second protein by means of a homobifunctional reagent, one cannot prevent the linking of the first protein to each other and of the second to each other. Heterobifunctional crosslinking reagents are, therefore, preferred because one can control the sequence of reactions, and combine proteins at will. Heterobifunctional reagents thus provide a more sophisticated method for linking two proteins. These reagents require one of the molecules to be joined, hereafter called Partner B, to possess a reactive group not found on the other, hereafter called Partner A, or else require that one of the two functional groups be blocked or otherwise greatly reduced in reactivity while the other group is reacted with Partner A. In a typical two-step process for forming heteroconjugates, Partner A is reacted with the heterobifunctional reagent to form a derivatised Partner A molecule. If the unreacted functional group of the crosslinker is blocked, it is then deprotected. After deprotecting, Partner B is coupled to derivatised Partner A to form the conjugate. Primary amino groups on Partner A are reacted with an activated carboxylate or imidate group on the crosslinker in the derivatisation step. A reactive thiol or a blocked and activated thiol at the other end of the crosslinker is reacted with an electrophilic group or with a reactive thiol, respectively, on Partner B. When the crosslinker possesses a reactive thiol, the electrophile on Partner B preferably will be a blocked and activated thiol, a maleimide, or a halomethylene carbonyl (eg. bromoacetyl or iodoacetyl) group. Because biological macromolecules do not naturally contain such electrophiles, they must be added to Partner B by a separate derivatisation reaction. When the crosslinker possesses a blocked and activated thiol, the thiol on Partner B with which it reacts may be native to Partner B.

An example of a heterobifunctional reagent is N-succinimidyl 3-(2-pyridyldithio)propionate (SPDP) (see for example Carlsson et al., 1978, Biochem. J., 173: 723-737). Other heterobifunctional reagents for linking proteins include for example succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC) (Yoshitake et al., 1979, Eur. J. Biochem, 101: 395-399), 2-iminothiolane (IT) (Jue et al., 1978, Biochemistry, 17: 5399-5406), and S-acetyl mercaptosuccinic anhydride (SAMSA) (Klotz and Heiney, 1962, Arch. Biochem. Biophys., 96: 605-612). All three react preferentially with primary amines (eg. lysine side chains) to form an amide or amidine group which links a thiol to the derivatized molecule (eg. a heterologous antigen) via a connecting short spacer arm, one to three carbon atoms long. Examples of heterobifunctional reagents comprising reactive groups having a double bond that reacts with a thiol group include SMCC mentioned above, succinimidyl m-maleimidobenzoate, succinimidyl 3-(maleimido)propionate, sulfosuccinimidyl 4-(p-maleimidophenyl)butyrate, sulfosuccinimidyl 4-(N-maleimidomethylcyclohexane-1-carboxylate and maleimidobenzoyl-N-hydroxysuccinimide ester (MBS). In a preferred embodiment, MBS is used to produce the conjugate. Other heterobifunctional reagents for forming conjugates of two proteins are described for example by Rodwell et al. in U.S. Pat. No. 4,671,958 and by Moreland et al. in U.S. Pat. No. 5,241,078.

In an alternate embodiment, a ubiquitin-antigen fusion protein is suitably expressed by a synthetic chimeric polynucleotide comprising a first nucleic acid sequence, which encodes an antigen corresponding to the target antigen, and which is linked downstream of, and in reading frame with, a second nucleic acid sequence encoding a ubiquitin or biologically active fragment thereof. In a preferred embodiment of this type, the second polynucleotide comprises a first nucleic acid sequence, which encodes an antigen corresponding to the target antigen, and which is linked immediately adjacent to, downstream of, and in reading frame with, a second nucleic acid sequence encoding a ubiquitin or biologically active fragment thereof. In another embodiment, the second polynucleotide comprises a first nucleic acid sequence, which encodes an antigen corresponding to the target antigen, and which is linked upstream of, and in reading frame with, a second nucleic acid sequence encoding a ubiquitin or biologically active fragment thereof. In yet another embodiment of this type, the second polynucleotide comprises a first nucleic acid sequence, which encodes an antigen corresponding to the target antigen, and which is linked immediately adjacent to, upstream of, and in reading frame with, a second nucleic acid sequence encoding a ubiquitin or biologically active fragment thereof. Preferably, but not exclusively, the ubiquitin-encoding nucleic acid sequence comprises the sequence set forth in SEQ ID NO: 1.

The invention further contemplates a synthetic construct (or expression vector), comprising a polynucleotide encoding a modified antigen as broadly described above, wherein said polynucleotide is operably linked to a regulatory polynucleotide. A polynucleotide encoding the modified antigen can be constructed from any suitable parent polynucleotide encoding an antigen that corresponds to the target antigen of interest. The parent polynucleotide is suitably a natural gene. However, it is possible that the parent polynucleotide is not naturally-occurring but has been engineered using recombinant techniques.

The regulatory polynucleotide suitably comprises transcriptional and/or translational control sequences, which will generally be appropriate for the host cell used for expression of the antigen-encoding polynucleotide. Typically, the transcriptional and translational regulatory control sequences include, but are not limited to, a promoter sequence, a 5′ non-coding region, a cis-regulatory region such as a functional binding site for transcriptional regulatory protein or translational regulatory protein, an upstream open reading frame, transcriptional start site, translational start site, and/or nucleotide sequence which encodes a leader sequence, termination codon, translational stop site and a 3′ non-translated region. Constitutive or inducible promoters as known in the art are contemplated by the invention. The promoters may be either naturally occurring promoters, or hybrid promoters that combine elements of more than one promoter. Promoter sequences contemplated by the present invention may be native to the host cell to be introduced or may be derived from an alternative source, where the region is functional in the host cell.

The synthetic construct of the present invention may also comprise a 3′ non-translated sequence. A 3′ non-translated sequence refers to that portion of a gene comprising a DNA segment that contains a polyadenylation signal and any other regulatory signals capable of effecting mRNA processing or gene expression. The polyadenylation signal is characterised by effecting the addition of polyadenylic acid tracts to the 3′ end of the mRNA precursor. Polyadenylation signals are commonly recognised by the presence of homology to the canonical form 5′ AATAAA-3′ although variations are not uncommon. The 3′ non-translated regulatory DNA sequence preferably includes from about 50 to 1,000 nucleotide base pairs and may contain transcriptional and translational termination sequences in addition to a polyadenylation signal and any other regulatory signals capable of effecting mRNA processing or gene expression.

In a preferred embodiment, the expression vector further contains a selectable marker gene to allow the selection of transformed host cells. Selection genes are well known in the art and will vary with the host cell used.

The expression vector may also include a fusion partner (typically provided by the expression vector) so that the recombinant polypeptide of the invention is expressed as a fusion polypeptide with said fusion partner. The main advantage of fusion partners is that they assist identification and/or purification of said fusion polypeptide. In order to express said fusion polypeptide, it is necessary to ligate an antigen-encoding polynucleotide according to the invention into the expression vector so that the translational reading frames of the fusion partner and the polynucleotide coincide. Well known examples of fusion partners include, but are not limited to, glutathione-S-transferase (GST), Pc portion of human IgG, maltose binding protein (MBP) and hexahistidine (HIS₆), which are particularly useful for isolation of the fusion polypeptide by affinity chromatography. For the purposes of fusion polypeptide purification by affinity chromatography, relevant matrices for affinity chromatography are glutathione-, amylose-, and nickel- or cobalt-conjugated resins respectively. Many such matrices are available in “kit” form, such as the QIAexpress™ system (Qiagen) useful with (HIS₆) fusion partners and the Pharmacia GST purification system. In a preferred embodiment, the recombinant polynucleotide is expressed in the commercial vector pFLAG as described more fully hereinafter. Another fusion partner well known in the art is green fluorescent protein (GFP). This fusion partner serves as a fluorescent “tag” which allows the fusion polypeptide of the invention to be identified by fluorescence microscopy or by flow cytometry. The GFP tag is useful when assessing subcellular localisation of the fusion polypeptide of the invention, or for isolating cells which express the fusion polypeptide of the invention. Plow cytometric methods such as fluorescence activated cell sorting (FACS) are particularly useful in this latter application. Preferably, the fusion partners also have protease cleavage sites, such as for Factor X_(a) or Thrombin, which allow the relevant protease to partially digest the fusion polypeptide of the invention and thereby liberate the recombinant polypeptide of the invention therefrom. The liberated polypeptide can then be isolated from the fusion partner by subsequent chromatographic separation. Fusion partners according to the invention also include within their scope “epitope tags”, which are usually short peptide sequences for which a specific antibody is available. Well known examples of epitope tags for which specific monoclonal antibodies are readily available include c-Myc, influenza virus haemagglutinin and FLAG tags.

The step of introducing into the host cell the recombinant polynucleotide may be effected by any suitable method including transfection, and transformation, the choice of which will be dependent on the host cell employed. Such methods are well known to those of skill in the art.

Recombinant polypeptides of the invention may be produced by culturing a host cell transformed with an expression vector containing nucleic acid encoding a polypeptide, biologically active fragment, variant or derivative according to the invention. The conditions appropriate for protein expression will vary with the choice of expression vector and the host cell. This is easily ascertained by one skilled in the art through routine experimentation. Suitable host cells for expression may be prokaryotic or eukaryotic. One preferred host cell for expression of a polypeptide according to the invention is a bacterium. The bacterium used may be Escherichia coli. Alternatively, the host cell may be an insect cell such as, for example, SF9 cells that may be utilised with a baculovirus expression system.

The recombinant protein may be conveniently prepared by a person skilled in the art using standard protocols as for example described in Sambrook, et al., MOLECULAR CLONING. A LABORATORY MANUAL (Cold Spring Harbor Press, 1989), in particular Sections 16 and 17; Ausubel et al., CURRENT PROTOCOLS IN MOLECULAR BIOLOGY (John Wiley & Sons, Inc. 1994-1998), in particular Chapters 10 and 16; and Coligan et al., CURRENT PROTOCOLS IN PROTEIN SCIENCE (John Wiley & Sons, Inc. 1995-1997), in particular Chapters 1, 5 and 6.

Alternatively, the modified antigen may be synthesised using solution synthesis or solid phase synthesis as described, for example, in Chapter 9 of Atherton and Shephard (supra) and in Roberge et al (1995, Science 269: 202).

3.2 Production of Unmodified Antigens (First Antigens)

Unmodified antigen, for use in producing the immunomodulatory compositions of the invention, may be prepared by any suitable technique. By “unmodified antigen” is meant any antigen, whether natural or synthetic that mimics or retains the intracellular proteolytic degradation of the target antigen. Accordingly, the unmodified antigen may be isolated from a natural source or may be prepared by recombinant techniques as is known in the art. Preferably, the unmodified antigen is prepared in recombinant form as for example described above for the modified antigens of the invention. For example, an unmodified antigen may be prepared by a procedure including the steps of (a) providing a polynucleotide encoding an unmodified antigen, which is operably linked to a regulatory polynucleotide; (b) introducing the polynucleotide into a suitable host cell; (c) culturing the host cell to express recombinant polypeptide from said polynucleotide; and (d) isolating the recombinant polypeptide.

The invention also envisions a synthetic construct, comprising a polynucleotide encoding an unmodified antigen? as broadly described above, wherein said polynucleotide is operably linked to a regulatory polynucleotide. A polynucleotide encoding the unmodified antigen can be constructed from any suitable parent polynucleotide, which codes for an antigen that corresponds to the target antigen of interest. The parent polynucleotide is suitably a natural gene. However, it is possible that the parent polynucleotide is not naturally-occurring but has been engineered using recombinant techniques.

4. Codon Optimisation of Antigen-Encoding Polynucleotides

The codon composition of antigen-encoding polynucleotides may be altered to enhance the expression of the antigen in a particular cell or tissue. Such codon optimisation is predicated on the replacement of existing codons in a parent polynucleotide with synonymous codons that have a higher translational efficiency in a chosen cell or tissue. Any suitable method of replacing synonymous codons for existing codons is contemplated by the present invention. For example, reference may be made to International Application Publication No WO 96/09378 which utilise such substitution to provide a method of expressing proteins of eukaryotic and viral origin at high levels in in vitro mammalian cell culture systems. Preferably, the codon composition of the polynucleotide is modified to permit selective expression of the antigen encoded thereby in a target cell or tissue of choice using methods as set forth in detail in International Application Publication Nos WO 99/02694 and WO 00/42215. In this regard, the present inventors were able to show in WO 99/02694 and in copending U.S. application Ser. No. 09/479,645 that there are substantial differences in the relative abundance of particular isoaccepting transfer RNAs in different cells or tissues of an organism (e.g., a mammal) and that this plays a pivotal role in protein expression from a coding sequence with a given codon usage or composition. Modification of the codons utilised in transgenes designed to generate translated proteins can lead to much higher and selective expression of particular genes in a cell or tissue of interest. Briefly, the method is based on the observation that translational efficiencies of different codons vary between different cells or tissues. Such differences can be exploited, together with codon composition of a gene, to regulate and direct expression of a protein or a functional fragment or epitope thereof to a particular cell or cell type, including cells in a selected tissue. Codons are selected such that the synonymous codon has a higher translational efficiency in a target cell or tissue relative to one or more other cells or tissues.

One or more codons in a gene may be substituted in order to target expression of the gene to particular cells or tissues. It is preferable but not necessary to replace all the existing codons of the parent nucleic acid molecule with synonymous codons having higher translational efficiencies in the target cell or tissue compared to the other cells or tissues. Increased expression can be accomplished even with partial replacement. Suitably, the replacement step affects 5%, 10%, 15%, 20%, 25%, 30%, more preferably 35%, 40%, 50%, 60%, 70% or more of the existing codons of the parent polynucleotide. The difference in level of protein expressed in the desired target cell or tissue from a synthetic polynucleotide, relative to that expressed in the other cells or tissues, depends on the percentage of existing codons replaced by synonymous codons and the difference in translational efficiencies of the synonymous codons in the target cell or tissue, relative to the other cells or tissues.

By optimising codon content, according to the procedures disclosed in WO 99/02694 and in copending U.S. application Ser. No 09/479645, it has been shown that a protein can be expressed from a synthetic polynucleotide in a target cell or tissue at levels greater than 10,000-fold over those expressed in another cell or tissue. A nucleic acid molecule, which has undergone such codon modification, is referred to herein as “optimised”.

5. Synthetic Constricts of the Invention

The invention also provides a synthetic construct for eliciting a humoral and a cellular immune response against a target antigen, comprising a first polynucleotide encoding a first antigen corresponding to the target antigen; and a second polynucleotide encoding a second antigen, corresponding to a modified form of the target antigen, whose rate of intracellular proteolytic degradation is increased, enhanced or otherwise elevated relative to the first antigen. In one embodiment the first polynucleotide and the second polynucleotide are operably linked to a regulatory polynucleotide. For example, the first and second polynucleotides may be expressed from a single promoter. In an alternate embodiment, the first polynucleotide and the second polynucleotide are operably linked to different regulatory polynucleotides. For example, the first and second polynucleotides may be expressed from different promoters.

The invention also contemplates a synthetic construct system for eliciting a humoral and a cellular immune response against a target antigen, comprising a synthetic construct comprising a first polynucleotide, which encodes a first antigen corresponding to the target antigen, and which is operably linked to a regulatory polynucleotide; and another synthetic construct comprising a second polynucleotide encoding a second antigen, which corresponds to a modified form of the target antigen, whose rate of intracellular proteolytic degradation is increased, enhanced or otherwise elevated relative to the first antigen, wherein said second polynucleotide is operably linked to a regulatory polynucleotide.

6. Delivery of Antigens to Cytosol

Modified and unmodified antigens according to the present invention or polynucleotides from which they are expressible may be linked to, or otherwise associated with, a cytolysin to enhance the transfer of the antigens into the cytosol of a target cell for delivery to the MHC class I pathway. Exemplary cytolysins include saponin compounds such as saponin-containing Immune Stimulating Complexes (ISCOMs) (see e.g., Cox and Coulter, 1997, Vaccine 15(3): 248-256 and U.S. Pat. No. 6,352,697), phospholipases (see, e.g., Camilli et al, 1991, J. Exp. Med. 173: 751-754), pore-forming toxins (e.g., an alpha-toxin), natural cytolysins of gram-positive bacteria, such as listeriolysin O (LLO, e.g., Mengaud et al, 1988, Infect. Immun. 56: 766-772 and Portnoy et al., 1992, Infect. Immun. 60: 2710-2717), streptolysin O (SLO, e.g., Palmer et al., 1998, Biochemistry 37(8): 2378-2383) and perfringolysin O (PFO, e.g., Rossjohn et al., Cell 89(5): 685-692). Where the target cell is phagosomal, acid activated cytolysins may be advantageously used. For example, listeriolysin exhibits greater pore-forming ability at mildly acidic pH (the pH conditions within the phagosome), thereby facilitating delivery of vacuole (including phagosome and endosome) contents to the cytoplasm (see, e.g., Portnoy et al., Infect. Immun. 1992, 60: 2710-2717).

The cytolysin may be provided together with one or both of the modified and unmodified antigens of the present invention in the form of a single composition or may be provided as a separate composition. In one embodiment, the cytolysin is fused or otherwise linked to one or both of said antigens, wherein the fusion or linkage permits the delivery of the antigen(s) to the cytosol of the target cell. In another embodiment, the cytolysin and antigen(s) are provided in the form of a delivery vehicle such as, but not limited to, a liposome or a microbial delivery vehicle selected from virus, bacterium, or yeast. Suitably, when the delivery vehicle is a microbial delivery vehicle, the delivery vehicle is nonvirulent. In a preferred embodiment of this type, the delivery vehicle is a nonvirulent bacterium, as for example described by Portnoy et al. in U.S. Pat. No. 6,287,556, comprising a first polynucleotide encoding a non-secreted functional cytolysin operably linked to a regulatory polynucleotide which expresses the cytolysin in the bacterium, and a second polynucleotide encoding one or more of said target antigens. Non-secreted cytolysins may be provided by various mechanisms, e.g. absence of a functional signal sequence, a secretion incompetent microbe, such as microbes having genetic lesions (e.g. a functional signal sequence mutation), or poisoned microbes, etc. A wide variety of nonvirulent, non-pathogenic bacteria may be used; preferred microbes are relatively well characterised strains, particularly laboratory strains of E. coli, such as MC4100, MC1061, DH5.alpha., etc. Other bacteria that can be engineered for the invention include well-characterised, nonvirulent, non-pathogenic strains of Listeria monocytogenes, Shigella flexneri, mycobacterium, Salmonella, Bacillus subtilis, etc. In a particular embodiment, the bacteria are attenuated to be non-replicative, non-integrative into the host cell genome, and/or non-motile inter- or intra-cellularly.

The delivery vehicles described above can be used to deliver one or more antigens of the invention to virtually any target cell capable of endocytosis of the subject vehicle, including phagocytic, non-phagocytic, pathogenic or diseased cells. Exemplary target animal cells include epithelial cells, endothelial cells, muscle cells, liver cells, pancreatic cells, neural cells, fibroblasts, tumour cells, leukocytes such as macrophages, neutrophils, B-cells, T-cells, monocytes, etc. In embodiments when the delivery vehicle is a microbe, the subject methods generally require microbial uptake by the target cell and subsequent lysis within the target cell vacuole (including phagosomes and endosomes). While phagocytic target cells generally provide for microbial uptake and lysis, for many cell types, it is necessary to provide the microbe (e.g., bacterium) with an invasin to facilitate or mediate uptake by the target cell and an autolysin to facilitate or mediate autolysis of the microbe within the target cell vacuole, as for example described by Portnoy et al. in U.S. Pat. No. 6,287,556.

7. Antigen-Presenting Cell Embodiments

The invention further provides a composition of matter for eliciting a humoral and a cellular immune response against a target antigen, comprising antigen-presenting cells which express a processed form of the first antigen as broadly described above, and a processed form of the second antigen as broadly described above, for presentation to, and modulation of, T cells. Antigen-primed antigen-presenting cells may be prepared by a method including contacting antigen-presenting cells with (1) a first antigen as broadly described above or a polynucleotide from which the first antigen is expressible, and (2) a second antigen as broadly described above or a polynucleotide from which the second antigen is expressible, for a time and under conditions sufficient to permit said first and second antigens to be internalised by the antigen-presenting cells; and culturing the antigen-containing antigen-presenting cells for a time and under conditions sufficient for the antigen(s) to be processed for presentation by the antigen-presenting cells. The antigen-presenting cells may be selected from dendritic cells, macrophages and B cells. In preferred embodiments of the invention, the antigen-presenting cells are dendritic cells.

7.1 Sources of Dendritic Cells

Dendritic cells can be isolated by methods known to those of skill in the art. Suitably, mammalian and preferably human dendritic cells are used from an appropriate tissue source, which is suitably blood or bone marrow. Dendritic cell precursors, from which the immature dendritic cells for use in antigen internalisation according to the invention, are present in blood as peripheral blood mononuclear cells (PBMCs). Although most easily obtainable from blood, the precursor cells may also be obtained from any tissue in which they reside, including bone marrow and spleen tissue. Peripheral blood precursors may be purified using monoclonal antibodies, density gradients or centrifugation or any combination of these. Circulating frequency may be increased in vivo using flt-3 ligand. When cultured in the presence of cytokines such as a combination of GM-CSF and IL-4 or IL-13 as described below, the non-proliferating precursor cells give rise to immature dendritic cells for use in this invention.

An exemplary method for culturing pluripotential PBMCs to produce immature dendritic cells is described by Albert et al. (International Publication WO 99/42564). In this respect, cultures of immature dendritic cells, ie. antigen-capturing phagocytic dendritic cells, may be obtained by culturing non-proliferating precursor cells (PBMCs) in the presence of cytokines which promote their differentiation. A combination of GM-CSF and IL-4 produces significant quantities of the immature dendritic cells, ie. antigen-capturing phagocytic or internalisation-competent dendritic cells. Other cytokines that promote differentiation of precursor cells into immature dendritic cells include, but are not limited to, IL-13.

Maturation of dendritic cells requires the addition to the cell environment, preferably the culture medium, of a dendritic cell one or more maturation factors which may be selected from monocyte conditioned medium and/or factors including TNF-α, IL-6, IFN-α and IL-1. Alternatively, a mixture of necrotic cells or necrotic cell lysate may be added to induce maturation. Maturation can be induced in vitro using plastic adherence, cytokines, LPS, bacteria, DNA containing CpG repeats, RNA or polyIC, CD40-ligation, necrotic cells. In this regard, reference may be made to Steinman et al. (International Publication WO 97/29182) who describe methods and compositions for isolation and maturation of dendritic cells.

Other methods for isolation, expansion and/or maturation of dendritic cells for the purpose of the present invention are described for example by Takamizawa et al. (1997, J Immunol, 158 (5): 2134-2142), Thomas and Lipsky (1994, J Immunol, 153 (9): 4016-4028), O'Doherty et al. (1994, Immunology, 82 (3): 487-93), Fearnley et al. (1997, Blood, 89 (10): 3708-3716), Weissman et al. (1995, Proc Natl Acad Sci USA, 92 (3): 826-830), Freudenthal and Steinman (1990, Proc Natl Acad Sci USA, 87 (19): 7698-7702), Romani et al. (1996, J Immunol Methods, 196 (2): 137-151), Reddy et al. (1997, Blood, 90 (9): 3640-3646), Thurnher et al. (1997, Exp Hematol, 25 (3): 232-237), Caux et al. (1996, J Exp Med, 184 (2): 695-706; 1996, Blood, 87 (6): 2376-85), Luft et al. (1998, Exp Hematol, 26 (6): 489-500; 1998, J. Immunol, 161 (4): 1947-1953), Cella et al. (1999, J Exp Med, 189 (5): 821-829; 1997, Nature, 388 (644): 782-787; 1996, J Exp Med, 184 (2): 747-572), Ahonen et al. (1999, Cell Immunol, 197(1): 62-72) and Piemonti et al. (1999, J Immunol, 162 (11): 6473-6481).

Alternatively, transformed or immortalised dendritic cell lines may be produced using oncogenes such as v-myc as for example described by Paglia et al. (1993, J Exp Med, 178 (6): 1893-1901).

7.2 Antigen Priming of Antigen-Presenting Cells

The amount of antigen to be placed in contact with antigen-presenting cells, which are preferably dendritic cells, can be determined empirically by persons of skill in the art. Antigen-presenting cells (which are preferably dendritic cells, are incubated with the antigen for 1-2 hr at 37° C. For most antigens, 10 μg/mL to 1-10 million dendritic cells is suitable for priming the dendritic cells. In a preferred embodiment, immature dendritic cells are utilised for the antigen internalisation.

The antigen(s) should be exposed to the antigen-presenting cells for a period of time sufficient for the antigen-presenting cells to internalise the antigen(s). The time necessary for the cells to internalise and present the processed antigen(s) may be determined using pulse-chase protocols in which exposure to antigen(s) is followed by a washout period. Once the minimum time necessary for cells to express processed antigen(s) on their surface is determined, a protocol may be used to prepare cells and antigen(s) for eliciting immunogenic responses. Those of skill in the art will recognise in this regard that the length of time necessary for an antigen-presenting cell to phagocytose or internalise a antigen may vary depending on the antigen used. Efficiency of priming of the antigen-presenting cells can be determined by assaying T cell cytotoxic activity in vitro or using antigen-presenting cells as targets of CTLs. Other methods known to practitioners in the art, which can detect the presence of antigen on the surface of antigen-presenting cells after exposure to one or more of the modified and unmodified antigens, are also contemplated by the presented invention.

In preferred embodiments where the antigen-presenting cells are dendritic cells, such cells have the capacity to efficiently present a processed form of the modified antigen and the unmodified antigen in the form of peptides on both MHC class I and class II molecules. Antigens are acquired by dendritic cells through the exogenous pathway by phagocytosis and, as a result, efficiently charge MHC class II molecules. Accordingly, both CD4⁺ T helper lymphocytes and CTL may be activated by dendritic cells presenting modified and optionally unmodified antigen in the context of MHC class II. These lymphocytes can provide critical sources of help, both for generating active CD8⁺ CTL and can in some circumstances be primed as CD4⁺ CTL with specificity for the target antigen during the acute response to antigen, and for generating the memory that is required for long term resistance and vaccination. Further, modified antigen and optionally unmodified antigen uptake and presentation by dendritic cells, allows these cells to tailor the peptides that are appropriate for an individuals MHC products, and increases the number of specialised stimulatory antigen-presenting cells. Moreover, dendritic cells can be charged with multiple antigens on multiple MHCs to yield polyclonal or oligoclonal stimulation of T cells. Thus, by using the antigens of the present invention to charge MEC class I and class II molecules, efficient T cell modulation in situ can be achieved.

8. Compositions

The modified antigens and unmodified antigens described respectively in Sections 3 and 4, the synthetic construct and synthetic construct system described in Section 5, and the antigen-primed antigen-presenting cells described in Section 7 (therapeutic/prophylactic agents) can be used as active ingredients for the treatment or prophylaxis of various conditions associated with the presence of a target antigen. These therapeutic/prophylactic agents can be administered to a patient either by themselves, or in compositions where they are mixed with a suitable pharmaceutically acceptable carrier and/or diluent, or an adjuvant.

The invention also encompasses a method for stimulating a patient's immune system, and preferably for eliciting a humoral and a cellular immune response against a target antigen, by administering to the patient a therapeutic agent or composition as described above. Such stimulation may be utilised for the treatment and/or prophylaxis of a disease or condition including, but not restricted to, a pathogenic infection (e.g. viral, bacterial, fingal, protozoan). Alternatively, the stimulation can be used to modulate an immune response to an autoantigen (e.g., associated with Rheumatoid arthritis).

Thus, the invention contemplates a method for treatment and/or prophylaxis of a disease or condition, comprising administering to a patient in need of such treatment a therapeutically/prophylactically effective amount of a composition as broadly described above. In one embodiment, the method comprises administering concurrently to the patient an unmodified antigen as broadly described above, or a polynucleotide from which the unmodified antigen is expressible, together with a modified antigen as broadly described above, or a polynucleotide from which the modified antigen is expressible. In another embodiment, the method comprises coadministering to a patient a polynucleotide from which said unmodified antigen is expressible, and a polynucleotide from which said modified antigen is expressible. In yet another embodiment, the method comprises coadministering to a patient said unmodified antigen and a polynucleotide from which said modified antigen is expressible. In still yet another embodiment, the method comprises concurrently administering to a patient a polynucleotide from which said unmodified antigen is expressible, together with said modified antigen. In a further embodiment, the method comprises coadministering to a patient said unmodified antigen and antigen-presenting cells which have been exposed to said modified antigen, or a polynucleotide from which said modified antigen is expressible, for a time and under conditions sufficient to express a processed form of said modified antigen for presentation to, and modulation of, T cells. In still a further embodiment, the method comprises administering concurrently to a patient antigen-presenting cells which have been exposed to said modified antigen, or a polynucle4otide from which said modified antigen is expressible, and to said unmodified antigen, or a polynucle4otide from which said unmodified antigen is expressible, for a time and under conditions sufficient to express a processed form of said modified antigen and a processed form of said unmodified antigen for presentation to, and modulation of, T cells.

Depending on the specific conditions being treated, therapeutic/prophylactic agents may be formulated and administered systemically or locally. Techniques for formulation and administration may be found in “Remington's Pharmaceutical Sciences,” Mack Publishing Co., Easton, Pa., latest edition. Suitable routes may, for example, include oral, rectal, transmucosal, or intestinal administration; parenteral delivery, including intramuscular, subcutaneous, intramedullary injections, as well as intrathecal, direct intraventricular, intravenous, intraperitoneal, intranasal, or intraocular injections. For injection, the therapeutic agents of the invention may be formulated in aqueous solutions, preferably in physiologically compatible buffers such as Hanks' solution, Ringer's solution, or physiological saline buffer. For transmucosal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are generally known in the art. Intra-muscular and subcutaneous injection is appropriate, for example, for administration of immunogenic compositions, vaccines and DNA vaccines.

The therapeutic/prophylactic agents can be formulated readily using pharmaceutically acceptable carriers well known in the art into dosages suitable for oral administration. Such carriers enable the compounds of the invention to be formulated in dosage forms such as tablets, pills, capsules, liquids, gels, syrups, slurries, suspensions and the like, for oral ingestion by a patient to be treated. These carriers may be selected from sugars, starches, cellulose and its derivatives, malt, gelatine, talc, calcium sulphate, vegetable oils, synthetic oils, polyols, alginic acid, phosphate buffered solutions, emulsifiers, isotonic saline, and pyrogen-free water.

Pharmaceutical compositions suitable for use in the present invention include compositions wherein the active′ ingredients are contained in an effective amount to achieve its intended purpose. The dose of agent administered to a patient should be sufficient to effect a beneficial response in the patient over time such as a reduction in the symptoms associated with the condition. The quantity of the therapeutic/prophylactic agent(s) to be administered may depend on the subject to be treated inclusive of the age, sex, weight and general health condition thereof. In this regard, precise amounts of the therapeutic/prophylactic agent(s) for administration will depend on the judgement of the practitioner. In determining the effective amount of the agent to be administered in the treatment or prophylaxis of the condition, the physician may evaluate tissue levels of a target antigen, and progression of the disease or condition. In any event, those of skill in the art may readily determine suitable dosages of the therapeutic agents of the invention.

Pharmaceutical formulations for parenteral administration include aqueous solutions of the active compounds in water-soluble form. Additionally, suspensions of the active compounds may be prepared as appropriate oily injection suspensions. Suitable lipophilic solvents or vehicles include fatty oils such as sesame oil, or synthetic fatty acid esters, such as ethyl oleate or triglycerides, or liposomes. Aqueous injection suspensions may contain substances which increase the viscosity of the suspension, such as sodium carboxymethyl cellulose, sorbitol, or dextran. Optionally, the suspension may also contain suitable stabilisers or agents which increase the solubility of the compounds to allow for the preparation of highly concentrated solutions.

Pharmaceutical preparations for oral use can be obtained by combining the active compounds with solid excipient, optionally grinding a resulting mixture, and processing the mixture of granules, after adding suitable auxiliaries, if desired, to obtain tablets or dragee cores. Suitable excipients are, in particular, fillers such as sugars, including lactose, sucrose, mannitol, or sorbitol; cellulose preparations such as, for example, maize starch, wheat starch, rice starch, potato starch, gelatin, gum tragacanth, methyl cellulose, hydroxypropylmethyl-cellulose, sodium carboxymethylcellulose, and/or polyvinylpyrrolidone (PVP). If desired, disintegrating agents may be added, such as the cross-linked polyvinyl pyrrolidone, agar, or alginic acid or a salt thereof such as sodium alginate. Such compositions may be prepared by any of the methods of pharmacy but all methods include the step of bringing into association one or more therapeutic agents as described above with the carrier which constitutes one or more necessary ingredients. In general, the pharmaceutical compositions of the present invention may be manufactured in a manner that is itself known, e.g., by means of conventional mixing, dissolving, granulating, dragee-making, levigating, emulsifying, encapsulating, entrapping or lyophilising processes.

Dragee cores are provided with suitable coatings. For this purpose, concentrated sugar solutions may be used, which may optionally contain gum arabic, talc, polyvinyl pyrrolidone, carbopol gel, polyethylene glycol, and/or titanium dioxide, lacquer solutions, and suitable organic solvents or solvent mixtures. Dyestuffs or pigments may be added to the tablets or dragee coatings for identification or to characterise different combinations of active compound doses.

Pharmaceutical which can be used orally include push-fit capsules made of gelatin, as well as soft, sealed capsules made of gelatin and a plasticiser, such as glycerol or sorbitol. The push-fit capsules can contain the active ingredients in admixture with filler such as lactose, binders such as starches, and/or lubricants such as talc or magnesium stearate and, optionally, stabilisers. In soft capsules, the active compounds may be dissolved or suspended in suitable liquids, such as fatty oils, liquid paraffin, or liquid polyethylene glycols. In addition, stabilisers may be added.

Dosage forms of the therapeutic agents of the invention may also include injecting or implanting controlled releasing devices designed specifically for this purpose or other forms of implants modified to act additionally in this fashion. Controlled release of an agent of the invention may be effected by coating the same, for example, with hydrophobic polymers including acrylic resins, waxes, higher aliphatic alcohols, polylactic and polyglycolic acids and certain cellulose derivatives such as hydroxypropylmethyl cellulose. In addition, controlled release may be effected by using other polymer matrices, liposomes and/or microspheres.

Therapeutic agents of the invention may be provided as salts with pharmaceutically compatible counterions. Pharmaceutically compatible salts may be formed with many acids, including but not limited to hydrochloric, sulphuric, acetic, lactic, tartaric, malic, succinic, etc. Salts tend to be more soluble in aqueous or other protonic solvents that are the corresponding free base forms.

For any compound used in the method of the invention, the effective dose can be estimated initially from cell culture assays. For example, a dose can be formulated in animal models to achieve a circulating concentration range that includes the IC50 as determined in cell culture (e.g., the concentration of a test agent, which achieves a half-maximal reduction in target antigen). Such information can be used to more accurately determine useful doses in humans.

Toxicity and therapeutic efficacy of the compounds of the invention can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., for determining the LD50 (the dose lethal to 50% of the population) and the ED50 (the dose therapeutically effective in 50% of the population). The dose ratio between toxic and therapeutic effects is the therapeutic index and it can be expressed as the ratio LD50/ED50. Compounds that exhibit large therapeutic indices are preferred. The data obtained from these cell culture assays and animal studies can be used in formulating a range of dosage for use in human. The dosage of such compounds lies preferably within a range of circulating concentrations that include the ED50 with little or no toxicity. The dosage may vary within this range depending upon the dosage form employed and the route of administration utilised. The exact formulation, route of administration and dosage can be chosen by the individual physician in view of the patient's condition. (See for example Fingl et al., 1975, in “The Pharmacological Basis of Therapeutics”, Ch. 1 p1).

Dosage amount and interval may be adjusted individually to provide plasma levels of the active compound(s) which are sufficient to maintain target antigen-reducing effects or effects that ameliorate the disease or condition. Usual patient dosages for systemic administration range from 1-2000 mg/day, commonly from 1-250 mg/day, and typically from 10-150 mg/day. Stated in terms of patient body weight, usual dosages range from 0.02-25 mg/kg/day, commonly from 0.02-3 mg/kg/day, typically from 0.2-1.5 mg/kg/day. Stated in terms of patient body surface areas, usual dosages range from 0.5-1200 mg/m²/day, commonly from 0.5-150 mg/m²/day, typically from 5-100 mg/m²/day.

Alternately, one may administer the agent in a local rather than systemic manner, for example, via injection of the compound directly into a tissue, often in a depot or sustained release formulation. Furthermore, one may administer the agent in a targeted drug delivery system, for example, in a liposome coated with tissue-specific antibody. The liposomes will be targeted to and taken up selectively by the tissue.

From the foregoing, it will be appreciated that the agents of the invention may be used as therapeutic or prophylactic immunomodulating compositions or vaccines. Accordingly, the invention extends to the production of immunomodulating compositions containing as active compounds one or more of the therapeutic/prophylactic agents of the invention. Any suitable procedure is contemplated for producing such vaccines. Exemplary procedures include, for example, those described in NEW GENERATION VACCINES (1997, Levine et al., Marcel Dekker, Inc. New York, Basel Hong Kong).

A preferred aspect of the present invention contemplates the use of nucleic acid compositions for the purpose of vaccination or immunomodulation. In this regard, a synthetic construct can be used to immunise a patient, which construct includes a polynucleotide encoding a modified antigen according to the invention, and/or a polynucleotide encoding an unmodified antigen according to the invention, wherein said polynucleotide(s) is operably connected to one or more regulatory sequences that direct expression of said polynucleotide(s) in said patient.

Typically, such constructs or vectors are derived from viral DNA sequences such as adenovirus, adeno-associated viruses, herpes-simplex viruses and retroviruses. Suitable immunomodulating vectors currently available to the skilled person may be found, for example, in Wu and Ataai (2000, Curr. Opin. Biotechnol. 11 (2): 205-208), Vigna and Naldini (2000, J Gene Med. 2 (5): 308-316), Kay, et al (2001, Nat. Med. 7 (1): 33-40), Athanasopoulos, et al. (2000, Int. J. Mol. Med. 6 (4): 363-375) and Walther and Stein (2000, Drugs 60 (2): 249-271).

Administration of the immunomodulating construct to a patient, preferably a human patient, may include delivery via direct oral intake, systemic injection, or delivery to selected tissue(s) or cells, or indirectly via delivery to cells isolated from the patient or a compatible donor. In a preferred embodiment, the immunomodulating construct is delivered intradermally. Delivery of said immunomodulating construct to cells or tissues of the patient or said compatible donor may be facilitated by microprojectile bombardment, liposome mediated transfection (e.g., lipofectin or lipofectamine), electroporation, calcium phosphate or DEAE-dextran-mediated transfection, for example. A discussion of suitable delivery methods may be found in Chapter 9 of CURRENT PROTOCOLS IN MOLECULAR BIOLOGY (Eds. Ausubel et aL; John Wiley & Sons Inc., 1997 Edition), for example, which is herein incorporated by reference.

The step of introducing the immunomodulating construct into a target cell or tissue will differ depending on the intended use and species, and can involve one or more of non-viral and viral vectors, cationic liposomes, retroviruses, and adenoviruses such as, for example, described in Mulligan, R. C., (1993). Such methods can include, for example:

-   A. Local application of the expression vector by injection (Wolff et     al., 1990), surgical implantation, instillation or any other means.     This method can also be used in combination with local application     by injection, surgical implantation, instillation or any other     means, of cells responsive to the protein encoded by the expression     vector so as to increase the effectiveness of that treatment. This     method can also be used in combination with local application by     injection, surgical implantation, instillation or any other means,     of another factor or factors required for the activity of said     protein. -   B. General systemic delivery by injection of DNA, (Calabretta et     al., 1993), or RNA, alone or in combination with liposomes (Zhu et     al., 1993), viral capsids or nanoparticles (Bertling et al., 1991)     or any other mediator of delivery. Improved targeting might be     achieved by linking the polynucleotide/expression vector to a     targeting molecule (the so-called “magic bullet” approach employing,     for example, an antigen-binding molecule), or by local application     by injection, surgical implantation or any other means, of another     factor or factors required for the activity of the protein encoded     by said expression vector, or of cells responsive to said protein. -   C. Injection or implantation or delivery by any means, of cells that     have been modified ex vivo by transfection (for example, in the     presence of calcium phosphate: Chen et al., 1987, or of cationic     lipids and polyamines: Rose et al., 1991), infection, injection,     electroporation (Shigekawa et al., 1988) or any other way so as to     increase the expression of said polynucleotide in those cells. The     modification can be mediated by plasmid, bacteriophage, cosmid,     viral (such as adenoviral or retroviral; Mulligan, 1993; Miller,     1992; Salmons et al., 1993) or other vectors, or other agents of     modification such as liposomes (Zhu et al., 1993), viral capsids or     nanoparticles (Bertling et al., 1991), or any other mediator of     modification. The use of cells as a delivery vehicle for genes or     gene products has been described by Barr et al., 1991 and by Dhawan     et al., 1991. Treated cells can be delivered in combination with any     nutrient, growth factor, matrix or other agent that will promote     their survival in the treated subject.

Immunomodulating compositions according to the present invention can contain a physiologically acceptable diluent or excipient such as water, phosphate buffered saline and saline. They may also include an adjuvant as is well known in the art. Suitable adjuvants include, but are not limited to: surface active substances such as hexadecylamine, octadecylamine, octadecyl amino acid esters, lysolecithin, imethyldioctadecylammonium bromide, N,N-dicoctadecyl-N′,N′bis(2-hydroxyethyl-propanediamine), methoxyhexadecylglycerol, and pluronic polyols; polyamines such as pyran, dextransulfate, poly IC carbopol; peptides such as muramyl dipeptide and derivatives, dimethylglycine, tuftsin; oil emulsions; and mineral gels such as aluminum phosphate, aluminum hydroxide or alum; lymphokines, QuilA and immune stimulating complexes (ISCOMS).

The modified antigen-primed, and optionally unmodified antigen-primed, antigen-presenting cells of the invention and antigen-specific T lymphocytes generated with these antigen-presenting cells can be used as active compounds in immunomodulating compositions for prophylactic or therapeutic applications. The primed cells, which are preferably mature dendritic cells, can be injected by any method that elicits an immune response into a syngeneic animal or human. Preferably, antigen-presenting cells are injected back into the same animal or human from whom the source tissue/cells was obtained. The injection site may be subcutaneous, intraperitoneal, intramuscular, intradermal, or intravenous. The number of antigen-primed antigen-presenting cells reinjected back into the animal or human in need of treatment may vary depending on inter alia, the antigen and size of the individual. This number may range for example between about 10⁴ and 10⁸, and more preferably between about 10⁶ and 10⁷ antigen-primed antigen-presenting cells (e.g., dendritic cells). The antigen-presenting cells should be administered in a pharmaceutically acceptable carrier, which is non-toxic to the cells and the individual. Such carrier may be the growth medium in which the antigen-presenting cells were grown, or any suitable buffering medium such as phosphate buffered saline.

In one embodiment, the antigen-primed antigen-presenting cells of the invention could also be used for generating large numbers of CD8⁺ or CD4⁺ CTL, for adoptive transfer to immunosuppressed individuals who are unable to mount normal immune responses. For example, antigen-specific CD8⁺ CTL can be adoptively transferred for therapeutic purposes in individuals afflicted with HIV infection (Koup et al., 1991, J. Exp. Med., 174: 1593-1600; Carmichael et al., 1993, J. Exp. Med., 177: 249-256; and Johnson et al., 1992, J. Exp. Med., 175: 961-971), malaria (Hill et al., 1992, Nature, 360: 434-439) and malignant tumours such as melanoma (Van der Brogen et al., 1991, Science, 254: 1643-1647; and Young and Steinman, 1990, J. Exp. Med., 171: 1315-1332).

In another embodiment, the immunomodulating composition of the invention is suitable for treatment or prophylaxis of a cancer. Cancers which could be suitably treated in accordance with the practices of this invention include cancers associated with a viral infection such as cervical cancer (e.g., papillomavirus infection) and Burkitt's lymphoma (e.g., Epstein Barr virus infection). Other virus associated cancers include, but are not restricted to, HTLV1 associated leukemia, Non Hodgkins lymphoma (EBV), anal cancer, skin cancer (BPV), hepatocellular carcinoma (HBV) and Kaposis sarcoma (HHV8).

In yet another embodiment, the immunomodulating composition is suitable for treatment or prophylaxis of a viral, bacterial or parasitic infection. Viral infections contemplated by the present invention include, but are not restricted to, infections caused by HIV, Hepatitis, influenza, Japanese encephalitis virus, Epstein-Barr virus and respiratory syncytial virus. Bacterial infections include, but are not restricted to, those caused by Neissenia species, Meningococcal species, Haemophilus species Salmonella species, Streptococcal species, Legionella species and Mycobacterium species. Parasitic infections encompassed by the invention include, but are not restricted to, those caused by Plasmodium species, Schistosoma species, Leishmania species, Trypanosoma species, Toxoplasma species and Giardia species.

The effectiveness of the immunization may be assessed using any suitable technique. For example, CTL lysis assays may be employed using stimulated splenocytes or peripheral blood mononuclear cells (PBMC) on peptide coated or recombinant virus infected cells using ⁵¹Cr labeled target cells. Such assays can be performed using for example primate, mouse or human cells (Allen et al., 2000, J. Immunol. 164(9): 4968-4978 also Woodberry et al., infra). Alternatively, the efficacy of the immunization may be monitored using one or more techniques including, but not limited to, HLA class I tetramer staining—of both fresh and stimulated PBMCs (see for example Allen et al., supra), proliferation assays (Allen et al., supra), ELISPOT assays and intracellular cytokine staining (Allen et al., supra), ELISA Assays—for linear B cell responses; and Western blots of cell sample expressing the synthetic polynucleotides. Particularly relevant will be the cytokine profile of T cells activated by antigen, and more particularly the production and secretion of IFN γ, IL-2, IL4, IL5, IL-10, TGFβ and TNF α.

9. Methods for Assessing Immunomodulation

An individual's capacity to respond to foreign or disease-specific antigens (e.g., viral antigens and cancer antigens) may be assessing whether those cells primed to attack such antigens are increased in number, activity, and ability to detect and destroy those antigens. Strength of immune response is measured by standard tests including: direct measurement of peripheral blood lymphocytes by means known to the art; natural killer cell cytotoxicity assays (see, e.g., Provinciali M. et al (1992, J. Immunol. Meth. 155: 19-24), cell proliferation assays (see, e.g., Vollenweider, I. and Groseurth, P. J. (1992, J. Immunol. Meth. 149: 133-135), immunoassays of immune cells and subsets (see, e.g., Loeffler, D. A., et al. (1992, Cytom. 13: 169-174); Rivoltini, L., et al. (1992, Can. Immunol. Immunother. 34: 241-251); or skin tests for cell-mediated immunity (see, e.g., Chang, A. E. et al (1993, Cancer Res. 53: 1043-1050).

The cytotoxic activity of T lymphocytes, and in particular the ability of cytotoxic T lymphocytes to be induced by antigen-presenting cells, may be assessed by any suitable technique known to those of skill in the art. For example, a sample comprising T lymphocytes to be assayed for cytotoxic activity is obtained and the T lymphocytes are then exposed to antigen-primed antigen-presenting cells, which have been caused to present antigen. After an appropriate period of time, which may be determined by assessing the cytotoxic activity of a control population of T lymphocytes which are known to be capable of being induced to become cytotoxic cells, the T lymphocytes to be assessed are tested for cytotoxic activity in a standard cytotoxic assay. Such assays may include, but are not limited to, the chromium release CTL assay known in the art.

The method of assessing CTL activity is particularly useful for evaluating an individual's capacity to generate a cytotoxic response against cells expressing tumour or viral antigens. Accordingly, this method is useful for evaluating an individual's ability to mount an immune response against a cancer or virus.

In order that the invention may be readily understood and put into practical effect, particular preferred embodiments will now be described by way of the following non-limiting examples.

EXAMPLES Example 1 Mice, DNA Immunisation and Cell Lines

Specific pathogen-free female BALB/c and C57BL/6 mice aged 6 to 8 weeks were purchased from the Animal Resource Centre (Perth, Australia) and were maintained under clean conditions in a conventional mouse house.

Female BALB/c and C57 BL/6 mice, 6 to 8 weeks old, were immunised by particle bombardment with DNA-coated gold beads (2 μg DNA/dose) using the helium-powered Helios Gene Gun delivery system (Bio-Rad Laboratories, Richmond, Calif., U.S.A.). DNA (1.0 μg) was coupled to 0.5 mg of 1.0-μm-diameter gold particles, as recommended by the manufacturer. DNA-coated microcarriers were delivered into the abdominal epidermis at a helium pressure setting of 400 psi.

A human papillomavirus (HPV) 16 E7 transduced EL-4 cell line, C2³⁶, and the parent cell line (EL-4) were maintained in complete RPMI-1640 medium plus 10% foetal bovine serum (CSL, Melbourne, Australia).

Example 2 Codon Replacements in the HPV6bL1, E7 and Ubiquitin Genes

The HPV6bL1, TV6b-E7 and the human ubiquitin gene sequences were modified to substitute preferred codons for rarely used codons, according to previously described methods¹². A polynucleotide encoding BPV6bL1 truncated of the C terminal 33 amino acids was made as a codon-modified construct (H6L1Δ) (SEQ ID NO: 9) and also with the native codons (6L1Δ) (SEQ ID NO: 7).

An HPV6bL1-E7 fusion gene (H6L1E7.1) (SEQ ID NO: 11) was constructed by adding to H6L1δ a codon-modified sequence corresponding to amino acids 2-50 of the HPV6b E7 protein. H6L1E7.2 (SEQ ID NO: 13) was similarly constructed by adding a polynucleotide encoding amino acids 49-98 of HPV6b E7, and H6L1-H16E7 (SEQ ID NO: 19) was constructed by adding a polynucleotide corresponding to the minimal H-2 D^(b) CTL epitope of HPV16 (RAHYNIVTF) (SEQ ID No. 29). Construction of codon-modified BPV1 L2 (SEQ ID NO: 23), termed HBL2, has been described previously¹².

A ubiquitin-HL1-16E7 fusion construct (SEQ ID NO: 15) was produced by adding a sequence encoding a ubiquitin monomer 5′ to the L1-16E7 gene construct. Codon-modified genes of the desired sequence were synthesised by Operon (Alameda, Calif., U.S.A.), and all sequences were verified by big dye terminator sequencing. Sequences for the seven novel codon-modified polynucleotide vaccine constructs used herein were deposited with GenBank under Accession Numbers AF322411-5 (SEQ ID NO:9, 11, 13, 15, respectively) and AF323508-9 (SEQ ID NO: 17 and 19, respectively).

Example 3 Plasmid Constructions

Primers were designed to allow cloning of gene constructs into eukaryotic expression plasmids. All primers coded for one flanking EcoRI or KpnI restriction site at their N-terminus, and for 18-24 nucleotides of the corresponding gene. These were used to amplify PV gene sequences by PCR. Amplified PCR products were cut with KpnI and EcoRI restriction enzymes and ligated to the pCDNA3 mammalian expression vector containing the simian virus 40 (SV40) ori (Invitrogen, Carlsbad, Calif., U.S.A.) to produce the corresponding expression plasmids.

Example 4 Measurement of Antibody Responses

Measurement of total VLP-specific IgG in serum was performed by capture ELISA, as previously described³⁷. To measure HPV6b L1 antibody against linear epitopes, HPV6b L1 VLPs were denatured by alkaline reduction (0.2M Na₂CO₃ buffer, pH 10.6, 0.01 M dithiothreitol) 38 and coated directly onto ELISA plates at a concentration of 20 μg/ml. For the L2 antibody assay (see Example 11, below), ELISA plates were coated with 50 μl of purified His-tag recombinant BPVL2 protein at a concentration of 10 μg/ml in 50 mM carbonate buffer, pH. 9.6. For the E7 specific antibody assay, Cos-1 cells (see Example 6, below) were transfected with pCDNA3E7³⁹ for 48 hours. Cell lysates were prepared in 0.5% NP-40, 0.1 M Tris-HCL (Ph. 8.5). Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was carried out using standard methods. Proteins were transferred to nitrocellulose membrane. Sera were applied diluted 1:100 in PBS with 5% non-fat dried milk. Secondary antibody was peroxidase-conjugated anti-mouse (Sigma, St Louis, Mo., U.S.A.), and was detected by ECL.

Example 5 Codon Modification Generates Increased Immunogenicity

To investigate the effect of codon modification on immunogenicity of a human papillomavirus 6 (BPV6) L1 capsid protein polynucleotide vaccine, plasmids were constructed to express HPV6b L1, utilising either the native nucleotide sequence (p6L1Δ) (SEQ ID NO: 7) or a sequence modified to encode the same L1 primary protein, using codons commonly found in highly expressed human genes (pH6L1Δ) (SEQ ID NO: 9). Both L1 gene constructs were truncated by 33 codon triplets at the C terminus. This removed a region encoding the L1 nuclear localisation signals¹⁶, which allows addition of sequences encoding defined T cell epitopes from papillomavirus (PV) non-structural proteins for therapeutic effect, while preserving the ability of the L1 protein to form virus-like particles (VLPs)¹⁷.

Plasmids were purified using a Qiagen Plasmid Mega Kit (Qiagen, Chatsworth, Calif., U.S.A.) and were dissolved in phosphate-buffered saline (PBS) at a concentration of 1 μg/μL.

Conformational antibody against HPV6b was detected after a single immunisation with pH6L1Δ (SEQ ID NO: 9), delivered intracutaneously on gold beads, and the antibody titre increased after a further immunisation (see FIG. 1 a). Antibody reactive with denatured HPV6b L1 protein was also observed, at lesser titre than antibody reactive with HPV6b VLPs (see FIG. 1 b). In contrast, no antibody specific for HPV6b VLPs or for denatured HPV6b L1 was found following immunisation with the non-codon-modified L1 gene p6L1Δ (SEQ ID NO: 7) (FIGS. 1 a and 1 b). Thus, a codon-modified L1 polynucleotide vaccine was significantly more immunogenic than the native gene, and induced antibody predominantly to conformational epitopes of the virus. Similar data with native (SEQ ID NO: 3) and codon modified (SEQ ID NO: 5) plasmids expressing a full length HPV6b L1 protein were also obtained.

Previous studies with PV L1 polynucleotide vaccines have shown that codon unmodified vaccines are relatively non-immunogenic, in keeping with the current findings. Repeated intranasal immunisation of mice with an HPV16 L1 polynucleotide vaccine induced serum IgG and vaginal IgA responses that were scarcely above background, although some T cell proliferation and cytokine release was observed in splenocytes from immunised animals exposed to particulate L1 VLP antigen¹³. Intravaginal immunisation of rabbits with HPV6b L1 DNA required cholera toxin to induce some VLP specific IgA antibody in vaginal secretions, whereas animals immunised intramuscularly with the same construct had no detectable serum L1 specific antibody by ELISA and low titre antibody by immunoblot¹⁴. CRPV L1 polynucleotide vaccines are, in contrast to HPV, immunogenic, whether delivered by im injection³² or intradermally³³. While CRPV is generally similar in codon usage to other PV genes, the CRPV L1 gene is relatively GC rich with a GC content approaching the mammalian genome consensus (Human consensus 52.5%; CRPV 47.7%; HPV6 42.5%), and several codons relatively infrequently used in mammalian genes are significantly less common in CRPV L1 than in BPV1, HPV6, or HPV16 (Table 1). Presumably, one or more of these codons are poorly translated in the cell types in which L1 expression is required for induction of antibody in vivo. Additionally, internal RNA sequences inhibitory to translation of PV L1 genes³⁴ might be less inhibitory in CRPV than in other PV genomes.

Example 6 Humoral Immunity in Mice Immunised with Chimeric L1-E7 Hybrid Polynucleotides

To induce immune responses that might be therapeutic as well as prophylactic for PV infection, chimeric polynucleotide vaccines were constructed by incorporating the L1 capsid gene (pH6L1Δ) (SEQ ID NO: 9) with segments of E7 (SEQ ID NO: 11 and 13), a non-structural protein of PV found abundantly in infected cells, added to the C terminus. Mice immunised with each of these chimeric codon-modified L1 polynucleotide vaccines developed high levels of virus specific antibody (see FIG. 1 c and 1 d). Induction of E7 specific immunity by the L1-E7 chimeric vaccines was tested using BPV6bE7 transfected Cos-1 cells as a source of HPV6b E7 protein. Immunoreactivity with a 14 kD protein, presumed to be E7, was observed in mice immunised with L1 chimeric polynucleotide vaccines which incorporated the N—or C-terminal region of HPV6bE7 (pH6L1E7.1 or pH6L1E7.2, SEQ ID NO: 11 and 13, respectively) (see FIG. 1 f). As expected, no reactivity with HPV6bE7 in serum from mice immunised with pH6L1Δ (SEQ ID NO: 9), or from non-immunised mice, was seen.

Example 7 Cell-Mediated Immunity in Mice Immunised with Chimeric L1-E7 Hybrid Polynucleotides

As therapeutic intervention for PV appears to require cell-mediated immune responses to PV proteins, induction of cellular immune responses by the polynucleotide vaccines was then measured. First, the induction of delayed type hypersensitivity (DTH) to the L1 capsid protein was examined. The DTH reaction was assayed by an ear-swelling test, as previously described⁴⁰, using purified HPV6b L1VLPs¹¹ as the challenge antigen. L1-specific DTH responses were observed to be induced by immunisation with codon-modified pH6L1Δ (SEQ ID NO: 9), and also by codon-modified L1 E7 chimeric vaccines pH6L1E7.1 and pH6L1E7.2 (SEQ ID NO: 11 and 13, respectively), but not by codon-unmodified p6L1Δ (SEQ ID NO: 7) or by the pCDNA3 vector (see FIG. 2 a).

The cytotoxic T lymphocyte (CTL) response induced to a dominant H-2^(b) restricted CTL epitope of HPV16 E7, incorporated in the codon-modified chimeric construct pH6L1-16E7 (SEQ ID NO: 19), was found to be relatively poor (see FIG. 2 b).

Example 8 Ubiquitination of 6L1 Improves CTL Response

To determine whether ubiquitination of the codon-modified 6L1 gene product could improve the CTL response, a vaccine was made in which a single copy of the ubiquitin gene was inserted, in frame, 5′ to the codon-modified chimeric L1-E7 gene (SEQ ID NO: 17).

Splenocytes were prepared from immunised animals and CTL activity was assessed after a 3 day in vitro re-stimulation with rIL-2 (Sigma), and peptide RAHYNIVTF (SEQ ID No. 29), as previously described⁴⁴. Assays were performed in triplicate, and spontaneous ⁵¹Cr release from the various targets did not exceed 15%.

A modified ELISPOT assay⁴¹ was used to detect HPV-16 E7-specific CD8+ T cells. Filtration plates (96-well) (Millipore, Bedford, Mass., U.S.A.) were coated with 10 μg/mL rat anti-mouse IFN-γ antibody (clone R4-6A2, Pharmingen, San Diego, Calif., U.S.A.) in 50 μL PBS. After overnight incubation at 4° C., the wells were washed and blocked with culture medium containing 10% foetal bovine serum. 1×10⁶ of fresh isolated spleen and lymph node cells were added to the well, along with 20 IU/mL IL-2. Cells were incubated at 37° C. for 24 hours either with or without 1 μg/mL HPV16 E7 specific H-2D^(b) CTL epitope (E7, amino acid 49-57). After culture, the plate was washed and then followed by incubation with 5 μg/mL biotinylated IFN-γ antibody (clone XMG1.2, PharMingen, Franklin Lakes, N.J., U.S.A.) in 50 μL in PBS at 4° C. overnight. After washing six times, 1.25 μg/mL avidin-alkaline phosphatase (Sigma) in 50 μL PBS was added and incubated for 2 hours at room temperature. After washing, spots were developed by adding 50 μL of 5-bromo-4-chloro-3-3-indolyl phosphate/nitroblue tetrazolium solution (Boehringer Manheim, Indianapolis, Ind., U.S.A.) and incubated at room temperature for 1 hour. The spots were counted using a dissecting microscope.

The ubiquitin-containing vaccine, in contrast to the construct without ubiquitin, induced a significant E7-specific CD8 T cell response (see FIG. 2 b).

Example 9 CTL Response Following Ubiquitination is Host-Protective

Mice were challenged with an E7-expressing tumour, in order to assess whether the observed improved CTL response was host protective. Mice were S.C.-challenged with 2×10⁶ cells/mouse TC-1 tumour cell⁴², in the scruff of neck, and tumour weight recorded 10 days after challenge, as previously described⁴³.

As can be seen in FIG. 2 c, mice immunised with ubiquitin-conjugated H6L1-16E7 (SEQ ID NO: 17) showed significant reduction in tumour weight, compared with animals immunised with the same construct without ubiquitin. These data confirmed that the induced cellular response was, indeed, host protective. Of interest, the ubiquitin-conjugated chimeric construct induced only low levels of HPV specific antibodies (refer to FIG. 1 e) when compared with the non-ubiquitin construct. A mixed polynucleotide vaccine comprising the codon modified L1-E7 with and without ubiquitin was, therefore, made to establish whether the mixture would convey the properties of both immunogens. Mice immunised with the mixture acquired both conformational and non-conformational antibody to L1 (FIG. 3 a,b) and developed IFN-γ secreting CD8⁺ cells in lymph node and spleen (FIG. 3 c), and were protected against tumour challenge (data not shown) confirming that the immune response to the mixed polynucleotide vaccine was as would be expected from the response to each of the two parts.

Example 10 HPV6bL1 Polynucleotide Vaccine Induces Neutralising Antibodies

To confirm that the various modified L1 vaccine constructs each induced PV neutralising antibody, sera were tested in a hemagglutination inhibition assay (HAI) shown to correlate with virus neutralisation¹⁸. The method used was as previously described¹⁸. Sera from mice immunised with each of the codon-modified and codon-modified chimeric constructs showed strong HAI activity (see FIG. 4), whereas no HAI activity were found in the sera from mice immunised with the unmodified L1 gene.

Example 11 Anti-BPVL2 Antibodies in Mice Immunised with an L2 Polynucleotide Vaccine

To confirm for a further PV gene that the immunogenicity of a polynucleotide vaccine could be enhanced by codon modification, mice were immunised with a codon-modified (SEQ ID NO: 23) or an unmodified (SEQ ID NO: 21) BPV1 L2 polynucleotide vaccine, or with a BPV1 L2-HPV16E7 fusion gene, also codon-modified or unmodified.

Mice immunised with codon-modified HBL2 (SEQ ID NO: 23) and IBL2E7 developed anti-BPVL2 antibodies, whereas mice immunised with a codon-unmodified L2 (SEQ ID NO: 21) gene did not (see FIG. 5), confirming that the immunogenicity of the L2 gene was also improved by codon modification.

The disclosure of every patent, patent application, and publication cited herein is hereby incorporated herein by reference in its entirety.

The citation of any reference herein should not be construed as an admission that such reference is available as “Prior Art” to the instant application

Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features. Those of skill in the art will therefore appreciate that, in light of the instant disclosure, various modifications and changes can be made in the particular embodiments exemplified without departing from the scope of the present invention. All such modifications and changes are intended to be included within the scope of the appended claims.

TABLE 1 Codons significantly less frequently used in CRPV L1 than in PV L1 genes poorly immunogenic as DNA vaccines. Occurrences in L1 Consensus Mammalian Codon CRPV HPV6 BPV1 Usage/1000 codons¹ TTG (Leu) 2 10 7 12.3 TTA (Leu) 3 14 8 7.2 AAT (Asn) 2 4 4 17.1 CGT (Arg) 1 4 2 4.6 ¹Codons encoding Leu occur as 98 of 1000, Asn as 37 of 1000, and Arg as 56 of 1000 codons when averaged across the mammalian GenBank database

1: Codons encoding Leu occur as 98 of 1000, Asn as 37 of 1000, and Arg as 56 of 1000 codons when averaged across the mammalian GenBank database

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The invention claimed is:
 1. A composition for eliciting a humoral and a cellular immune response against a target antigen, comprising a first antigen corresponding to the target antigen, or a polynucleotide from which the first antigen is expressible, together with a second antigen corresponding to the target antigen and including an intracellular degradation signal, wherein the intracellular degradation signal is fused or conjugated to said second antigen, and wherein the rate of intracellular proteolytic degradation of the second antigen is increased, enhanced or otherwise elevated relative to the first antigen, or a polynucleotide from which the second antigen is expressible.
 2. The composition of claim 1, wherein said intracellular proteolytic degradation is proteasome-mediated.
 3. The composition of claim 1, wherein said intracellular proteolytic degradation is ubiquitin-mediated.
 4. The composition of claim 1, wherein said intracellular degradation signal is selected from the group consisting of a destabilising amino acid at the amino-terminus of said second antigen, a ubiquitin acceptor, a ubiquitin, and a combination of these.
 5. The composition of claim 4, wherein said intracellular degradation signal is a destabilising amino acid selected from isoleucine and glutamic acid.
 6. The composition of claim 4, wherein said intracellular degradation signal is a destabilising amino acid selected from histidine, tyrosine and glutamine.
 7. The composition of claim 4, wherein said intracellular degradation signal is a destabilising amino acid selected from aspartic acid, asparagine, phenylalanine, leucine, tryptophan and lysine.
 8. The composition of claim 4, wherein said intracellular degradation signal is a destabilising amino acid being arginine.
 9. The composition of claim 1, wherein said intracellular degradation signal comprises a destabilising amino acid at the amino-terminus of said second antigen, and wherein said second antigen is fused or otherwise conjugated to a masking entity, which masks said amino terminus so that when unmasked said second antigen will exhibit the desired rate of intracellular proteolytic degradation.
 10. The composition of claim 9, wherein said masking entity is cleavable by an endoprotease.
 11. The composition of claim 4, wherein said intracellular degradation signal comprises an ubiquitin acceptor.
 12. The composition of claim 11, wherein said ubiquitin acceptor comprises one or more amino acid residues having an epsilon amino group.
 13. The composition of claim 11, wherein said ubiquitin acceptor comprises one or more lysine residues.
 14. The composition of claim 11, wherein said ubiquitin acceptor comprises one or more lysine residues present in a sufficiently segmentally mobile region of said second antigen.
 15. The composition of claim 4, wherein said intracellular degradation signal comprises a ubiquitin or biologically active fragment thereof.
 16. The composition of claim 1, wherein said first antigen retains greater than about 50% of its tertiary structure after about 3 minutes at intracellular or intracellular-like conditions.
 17. The composition of claim 1, wherein the intracellular half life of said first antigen is greater than about 3 minutes.
 18. The composition of claim 1, wherein the intracellular half life of said second antigen is less than about 3 minutes.
 19. The composition of claim 1, wherein the level of proteolytic degradation of said second antigen is at least about 5% greater than that of said first antigen.
 20. The composition of claim 1, wherein said target antigen corresponds to at least a portion of a structural protein.
 21. The composition of claim 20, wherein said structural protein is a structural protein of a pathogenic organism.
 22. The composition of claim 20, wherein said structural protein is a viral protein.
 23. The composition of claim 1, wherein said target antigen corresponds to at least a portion of a viral capsid protein.
 24. The composition of claim 23, wherein said viral capsid protein is from a crystalline virus.
 25. The composition of claim 23, wherein said viral capsid protein is selected from the group consisting of the L1 and/or L2 proteins of papillomavirus, VP 1-3 of polyomavirus, VP 1-6 of blue tongue virus, Hepatitis B surface antigen, Hepatitis C surface antigen, the capsid proteins of Parvovirus, the capsid proteins of Yeast Ty particles, the capsid proteins of Retroviruses, the capsid proteins of Rotavirus, the capsid proteins of Coronaviruses, and the capsid proteins of Adenovirus.
 26. The composition of claim 23, wherein said viral capsid protein is a papillomavirus capsid protein.
 27. The composition of claim 23, wherein said viral capsid protein is selected from the L1 and L2 capsid proteins of a papillomavirus.
 28. The composition of claim 1, further comprising an adjuvant.
 29. The composition of claim 28, wherein the adjuvant delivers said second antigen to the class I major histocompatibility (MHC) pathway.
 30. The composition of claim 28, wherein the adjuvant is an ISCOM.
 31. The composition of claim 28, wherein the adjuvant is a cytolysin, which mediates delivery of the antigens to the cytosol of a target cell.
 32. The composition of claim 28, wherein the adjuvant is a cytolysin, which is linked to, or otherwise associated with, one or both of said antigens.
 33. The composition of claim 28, wherein the adjuvant is a listeriolysin.
 34. A composition of matter for eliciting a humoral and a cellular immune response against a target antigen, comprising antigen-presenting cells which have been contacted with a first antigen corresponding to the target antigen or with a polynucleotide from which the first antigen is expressible, and with a second antigen corresponding to the target antigen and including an intracellular degradation signal, wherein the intracellular degradation signal is fused or conjugated to said second antigen, and wherein the rate of intracellular proteolytic degradation is increased, enhanced or otherwise elevated relative to the first antigen or with a polynucleotide from which the second antigen is expressible, for a time and under conditions sufficient to express a processed form of said first antigen, and a processed form of said second antigen, for presentation to, and modulation of, T cells.
 35. The composition of matter of claim 34, wherein the antigen-presenting cells are selected from dendritic cells, macrophages and B cells.
 36. The composition of matter of claim 34, wherein the antigen-presenting cells are dendritic cells.
 37. The composition of matter of claim 34, further comprising an adjuvant.
 38. The composition of matter of claim 34, wherein said T cells are cytotoxic T lymphocytes (CTLs).
 39. The composition of claim 20, wherein the structural protein is from a Herpesvirus.
 40. The composition of claim 39, wherein the structural protein is a glycoprotein D (GpD).
 41. The composition of claim 1, wherein the polynucleotide from which the first antigen is expressible and/or the polynucleotide from which the second antigen is expressible are codon optimized.
 42. The composition of claim 41, wherein the target antigen is a Herpesvirus antigen.
 43. The composition of claim 42, wherein the target antigen is glycoprotein D (GpD). 